This page contains a photograph which is one of several belonging to the photo gallery pages which are part of several pages relating to the invention of the world's first automatic totalizator in 1913 and Automatic Totalisators Limited, the company founded to develop, manufacture and export these systems. It also describes the first computer based totalisator system in the Southern Hemisphere, which replaced a Julius electromechanical totalisator at Harold Park in Sydney. Finally there are papers presented at a Decus conference describing the software and hardware design of the PDP8 based totalisator systems.

Copyright © 1997 - 2015 Email - totehis@hotmail.com


Historic Electromechanical Computing + PDP8 computer succesor

This is a Julius Tote, Raceday Control Console at Harold Park in 1958. The Tote Control Console was used to set and display variables such as race number, field size, scratchings and the number of place dividends. It also provides operational coordination between the machine room staff and the operations control staff. It also controlled the start and stop of selling operations. When the large knob in the middle of the Tote Control Console control panel was rotated clockwise the race number was incremented. This caused a barrel with the race number type to be rotated to the next number in every TIM. All the TIMs (Ticket Issuing Machines) clanked in unison as this selection was made. The scratching switches introduced an open circuit in the escapement coil circuits in the adder corresponding to the scratched runner. The white parts of the upper section are lamp boxes and bulbs illuminate the appropriate information when it is in operation. These devices were replaced by a computer application in the digital minicomputers that replaced these systems. More after the image...

Electromechanical tote Raceday Control Console

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Photo by CAMERACRAFT PTY.LTD. Crane Place Phone: BU 1594

In Brisbane, my domain, these devices and the other tote facilities were replaced by PDP11 based computer totes which I worked on. The application which replaced these hardware Raceday Control Consoles was named, you guessed it, the RDC for Raceday Control Console. When the PDP11 system was replaced by a VAX based system this application ended up called the TCC or Tote Control Console. In Brisbane this transition from electromechanical to computers took place later than many other tracks which first transitioned to a PDP8 computer based system.

The first transition Electromechanical to Digital Computers

I have included the following information from Rob Stone who worked on the PDP8 installations at Harold Park and Wentworth Park, which in the case of the former was nine years prior to the transition in Queensland, which I was a part of. The world's first of these electronic totes was developed by ATL for the New York Racing Association at Aqueduct. To read about this system, have a look at Aqueduct in the Automatic Totalisators in America chapter. It seems appropriate to present it here, as Rob mentions the Tote Control Console. Unlike the systems in Brisbane, Harold Park had an intermediate step prior to implementing PDP11 based totes and that was a PDP8 based tote system, the subject of Rob's anecdote. The Tote Control Console Rob is referring to, is not yet a pure software application but is a custom built console that performs the function of the Tote Control Console in the image and more, which Rob describes below. There is a direct link between Rob's information and the image above as the Tote Control Console he is referring to actually replaced the TCC at Harold Park shown in this image. My short time at Harold Park, starting with an introduction to Totalisator Operations and later repairing difficult to identify faults, was associated with the PDP11 computer tote that replaced the PDP8 system Rob is writing about. Another connection between the Julius Tote and Rob's PDP8 system, is that this computer based totalisator unlike its successor, spent more time superseding Julius Totes. As a consequence, an electronic device called a scanner was developed to interface the PDP8 systems with Julius Tote electromechanical TIMs. These electronic scanners replaced the Julius Tote front end system of the same name and interfaced to the PDP8s instead of the electromechanical shaft adders. Hence this PDP8 based system at Harold Park was capable of interfacing to the old J8 TIMs (Ticket Issuing Machines). I do not know if this feature was used at Harold Park. I have read that 114 new J11 TIMs were part of this new system. The J11s were specially developed for use with minicomputer systems. There were some J15s included in this project as well. The new system operated on Win Place Quinella and Doubles pools. To read about the J11 see A J11 TIM which is one of the images in the Photo Gallery Continued chapter.

Rob's Indicator Chaos anecdote, is very interesting to me, as it illustrates a basic principle regarding testing software before it goes live. This principle is that no amount of software testing, will identify all software bugs. When performing rigorous software testing, which is essential, there comes a time when you go beyond the law of diminishing returns. Once this point is passed you start dreaming up nightmare scenarios that will never bite you in operations incurring unfruitful expenditure. In other words there is a practical time when you have to go live with a new computer system to see what real problems remain. I am convinced that many computer systems retire with undiscovered bugs, as a result of a scenario envisaged and catered for in the software design, which never eventuates in the lifespan of the system, leaving the associated code never used. The problem Rob relates, interestingly enough, is one that I regard as one of those nightmare scenarios that would never have been dreamt up during the testing phase. The ultimate success of a system depends on how the problems revealed after going live are dealt with. It is the sort of action that Rob took, that resulted in the problem being rectified quickly and that, is essential for the ultimate success of a system. Oh and a bit of luck is very helpful, as Rob points out, as his problem manifested itself at the end of a race meeting, minimising the impact duration. Finally, he makes a reference to a well known totalisator operations problem, that if punters can't see the odds they don't bet.

Rob Stone's memories of the Harold Park PDP8 totalisator

I worked for ATL for 3 years, from Jan. 1970 to late 1972, initially as a Tote System Installation Engineer under Peter Rolls, and later in the Research Dept under George Klemmer.

I was given responsibility for installing the computer systems at Harold Park and Wentworth Park, supported by Peter Rolls, Ron Hood, Kevin Franks etc. in Installation, George Klemmer and team in Research, Dick Sterndale-Smith and programming team under George, Neville Mitchell Alf Lesins and team in the Drawing Office, and Alan Lakeman Bill Johnson and team on track.

After Harold Park was up and running, as far as I can remember, there were very few operational dramas, except for one memorable Saturday night.

The dog meeting was going smoothly, right up until 5 minutes before the last race (Race 10). This was when the TAB off-course betting data was entered into the on-course pools before each race, by an operator using an old ASR-33 teletypewriter (you remember them, don't you?).

Suddenly, absolute chaos descended as all the odds display boards on course "went crazy". Random draft dividends were displayed as the updates rippled down each column on the boards, then were overwritten as it went back to the start immediately and clobbered that data with further random dividends. This is all just as the majority of punters were waiting to see the changed odds after the off-course betting was added, before placing their final bets.

Very soon, Alan Lakeman and co. burst into the computer room, naturally demanding "Rob, what's going on???". I had already had time to take the first course of action, which was to take the B computer off-line, see no effect, put it back on-line, then take the A computer off-line, and (unfortunately) see no effect there either.

Of course, everyone wanted to know "How can the punters place their bets if they can't see the odds?" Unfortunately, the answer was: Either they have to go on the last displayed odds, or sorry, they don't bet.

As both computers were issuing chaotic but identical behaviour, I'd had to conclude that it was a software problem, and told Alan this. I said that therefore there was nothing else that could be done at the time, but just to keep our fingers crossed and hope that that the betting data stored in memory was safe (no disks in those days), and that the computers would stop accepting bets when the race started, and could then calculate the right dividends when needed. Fortunately (phew!), it was the last race of the night, everything else except the odds indicator boards appeared to function OK, and the race and night completed successfully.

Also fortunately, I had been able to observe exactly what had happened just prior to the calamity, and reported the details (I think with a printed memory dump), to Dick S-S first thing Monday morning, who was straight onto it. In entering the off-course betting info on the ASR-33, the operator had made a mistake, and had gone into a 'correct' or 'edit' mode, using 'Backspace'(s) etc. Unfortunately while in this mode, she made another error (probably under the pressure of hurrying before betting closed), and tried to correct that. And that's when "all hell done broke loose, boy".

In all the software testing that had been done, that was one combination of events that hadn't been anticipated, and the program tried to store part of the double-corrected data in the area of memory where the indicator board update program code resided - thus sending that software routine haywire. Also fortunately, that routine was the last in the memory map, and so other program code had not been affected.

Happy ending - The problem was fixed promptly by our software colleagues, and I don't recall any other significant incidents during the commissioning and hand-over periods at both tracks.

Webmaster's note: Rob's crippling fault caused by a software routine overwriting memory dedicated to storing instructions, reminds me of a similar problem in Brisbane. It was a bug overwriting a critical variable storing the Win Pool Grand Totals, resulting in intermittently displayed erroneous massive investments, on CCTV and Indicator displays around the track. I remember it well as it was difficult to isolate, as it was not possible to reproduce the symptoms in a test environment. We had J11 chip based PDP11s acting as protocol converters and the problem was in the firmware of these devices. These protocol converters converted TAB synchronous HDLC protocol, to the on course asynchronous digital communications protocol. This link sent the on course pool figures to the TAB and the TAB returned the figures for the whole of Queensland.
This was a significant problem, as it had the propensity to encourage punters to wager much more than they would have otherwise, unless they realised these massive investment figures on display were erroneous. Unlike Rob's condition, this problem manifest itself on multiple occasions and at the most undesirable times, only at big meetings. As it was not possible to recreate the symptoms, the only means of resolving the problem was to run versions of the application with debug code I had written to report pertinent parameters whilst running live at these big meetings. I determined that we were not receiving any odds messages with inflated win pool GTs from the TAB. The incoming messages from the TAB were being stored in a forward linked closed loop linked list. I implemented some debug code to report on parameters associated with this list.
Analysing the resulting debug information, it became obvious that under normal operations the linked list never wrapped around. The wrap around feature was only used if the reading procedure did not catch up with the writing procedure before the writing procedure got to the end of the buffer. Furthermore the corrupted win pool grand totals only occurred when a wrap around occurred after getting to the end of the buffer and starting at the beginning overwriting already processed messages. Consequently I scrutinised the software that manages the wrap around. I found that the writing procedure would overflow the end of the buffer by two bytes before wrapping around. The two extra bytes overwrote a word allocated to the variable used to store the Win Pool GT. The firmware source was changed to wrap around at the real buffer limit and the problem was solved.

And just reflecting on (gentleman) Alan Lakeman at Harold Park, I recalled a conversation with him that will stay with me forever:
Rob (reporting an equipment problem): "It's not working".
Alan: "What do you mean it's not working?"
Rob: "It's cactus f**ktus".
Alan (feigning shock & horror): "Rob! I'll have you know that I'm a lay preacher!"

I'll always remember the look of mock horror and indignation on Alan's face, before we both fell about laughing ... A memorable incident for me.

Rob Stone working on the PDP8 based totalisator at Harold Park Rob Stone with Duplex PDP8 system at Harold Park 1970


Photo supplied by Rob Stone:

The PDP8 based totalisator system shown above was Australia's first computer based totalisator system. Furthermore it was the first computer based totalisator system in the Southern Hemisphere.

(Webmaster's note: I love this image! Although I started with Automatic Totalisators on the following generation of computer totes based on the PDP11, this makes me feel completely at home. The computer consoles, the register lights, the paper-tape readers, the workbench, the paper-tape programs, the notes, the Biro, the documentation, the reel of wirewrap wire, the screwdrivers, the solder sucker, the Tektronix CRO (Cathode Ray Oscilloscope), standing on the floor on the near side of the chair, slightly under the bench, a very familiar workplace. The Tektronix 465 is a model I have spent much of my life attached to, it could be me in this image! Home Sweet Home! In all the staged publicity and sales photos, it is all clinically clean, however this image shows it the way it was for the engineering staff and represents the workplace that I spent far too much of my life in! )

Workday at Harold Park

The systems at Harold Park and Wentworth Park used duplex or twin PDP-8/I's, each with 16K words of memory. (Note: that's only approx 16,000 x 12-bit words to store all of the program, the variables, and all the betting data!). But as the interfacing to PDP-11s was developed during my 3 years at ATL, I believe that the following tote systems manufactured were soon based on the PDP-11s (the first being the PDP-11/20s).

The photo above was a real 'on-the-job' working snapshot in time. As Brian mentioned above, all of the tools visible in the photo - from the small spool of wirewrap wire, to the Tektronix 'scope almost hidden from view, indicate that it was probably in Nov. or Dec. 1970, during the installation and testing phase, before Harold Park went live in Dec. that year. The area I'm working on was a wire-wrapped panel which held the DEC discrete component R-series and W-series logic cards that interfaced the computers into the 'twin' configuration, and provided the latching and buffering of data from the computers, for handling by the other cabinets in the system. The other cabinets as I recall were, from the left: 1) The "Interface", which defined and handled which computers were on-line, and interfaced to the TCC (Tote Control Console) and the following equipment; 2) Two electronic Scanners, each of which was a cabinet of R- and W- logic cards (in a wirewrap panel) that scanned 64 TIMs, to see if any had grounded their 'bid' wire, then controlled them; 3) The BCU (indicator Board Control Unit), which had logic boards for latching data and selecting the lampboxes to be updated next, and also the relays that released the latching voltage from each lampbox group in turn (which dropped out the lampbox relays and hence their displayed digits), before a digit code was applied to each selected lampbox, if it was not to be blank. (Webmaster's note: The Interface panel is shown in the image below. It can also be seen in the image above where the first two control panels from the left, above the desk with papers on it, are the PDP8 consoles and the third panel is the Interface panel, finally the last one in view is one of the scanners.)

When being updated, each lampbox would receive a "2 out of 5" code on 5 parallel wires, which then displayed one of the 10 digits, 0 to 9. The "2 out of 5" code was a safety feature so that if a fault occurred activating (say) 1 or 3 of the 5 data lines, an irregular light pattern would be displayed (indicating an error), rather than displaying the wrong odds digit.

The TCC at that time was the physical input device that controlled the tote operation, after the programs were started in both computers. It was a neat, smart-looking desk-top panel, on about a 20 degree slope towards the front, fitted into a shallow housing about 2 ft wide, by say 15 - 18 inches deep, a few inches high at the front and about 6-7 in. high at the back. It had the full complement of illuminated push-buttons to indicate Race No., non-scratched starters, which pools were active, 'Start' and 'Stop' betting, 'Calculate Divs' when the results were official, etc. It sat on the bench opposite the computer system, next to the wide computer room window, where the operator could see race starts, 'Results Official' type indicators, etc

When a TIM locked in a bet request, it would ground its bid wire (1 for each machine), seeking access to the Scanner mentioned above. The Scanner would cycle around its 64 TIMs in turn (at the rate of about 5000 checks per second), and when it found a 'bid', it would stop on that TIM and provide an enabling voltage to the TIM, which gated its bet data on to 3 or 4 groups of 8 parallel wires (no serial communications at ATL at that stage), using a "3 out of 8" code for each significant TIM figure. The Scanner would then interrupt whichever computers were on-line and present the data for processing by the computers. Each computer would separately analyse the data bid from the TIM, and issue an 'Accept' or 'Reject' independently to the Scanner. If the responses agreed, the Scanner would issue either a 'Confirm' to the TIM and the ticket would be printed, or a 'Reject' and the TIM keys would be released with no ticket printed.

If the responses disagreed, or if no response was received from 1 computer within the time allowed, the Scanner would freeze, with bid data and the 2 responses displayed for the engineer to analyse. At which point, 64 TIMs were being held up, and the engineer had to quickly look at the bid data, assess whether it was a valid bet or not, whether betting was still current on that race or not, decide which computer was right, and take the other computer off-line with the flick of a switch on the Interface. That allowed the ticket to be accepted or rejected by just one computer, and freed the Scanner to move on to checking the other 63 TIMs.

As the computer processing time for each ticket was a small fraction of the time taken to actually print a ticket, and because each Scanner could move on to the next TIM as soon as it allowed a TIM to latch the Accept or Reject response, from memory, a Scanner could issue responses to all 64 connected TIMs within 1 to 2 seconds, even if all 64 had locked in a bet bid at virtually the same time.

On a software note, each computer in the duplex or twin system ran independently, but each computer set and cleared a flag which was incorporated into a synchronisation loop. My understanding of the mainline logic was that it consisted of a list of checks for inputs from all of the connected system equipment described above, as well as housekeeping tasks, (recalculating odds, printing betting and dividends information after a race, etc), plus the setting, checking and clearing of the sync flags. The loop was used as it was very important that each computer saw the same information at exactly the same time (or as closely as was possible), so that there wasn't a situation where the computers were processing bids from 2 different Scanners at the same time (as both would lock up waiting for the other computer), or where one computer could process a bet just before the "Stop Betting" signal while the other processed the same bet just after the "Stop". So at the start of the sync loop, each computer would set its sync flag, then wait (probably a very short time) for it to see from the Interface that the other computer had set its flag. At that point, each would clear its own flag and move off in 'lock-step' down the mainline program code, processing inputs and outputs as it went, until it came back to the 'top' of the sync loop, to repeat the process again.

However, I have digressed. Back to the photo ....

As wiring or design faults were found in our testing, it was necessary for the Engineer (yours truly in this case) to work out the change needed, remove the incorrect wire-wrapped connections, put the new ones in using a wirewrap gun, and re-test to see if that had fixed the problem - as well as checking that I hadn't added a new fault.

Seeing the complement of tools and equipment in the image, my guess is that the photo has caught a "technical field change" in progress at the time it was taken. If a change merely corrected a wiring error, where the connections didn't match the wiring diagrams (normally 20 to 36 x A3 pages per unit), it was just a matter of fixing the connections. If the wiring had been correct, but the logic needed changing to achieve the objective, I'd also mark up a copy of the wiring page(s) and send it(them) back to Neville in the Drawing Office to be updated and re-issued.

A Tricky Printing Problem

While integrating and testing the Harold Park system in the front test room at Meadowbank, before it was moved to H.P., a highly unusual printing problem turned up.

The symptoms were (are you ready for it?): All printouts from the tote software would print reliably on the DEC line printer (80 columns - I think it was imaginatively labelled as an 'LP-80'), except for when a prior page printed on less than half the page, and was followed by a 'Form Feed' command (skip to the start of the next page), the first line of print on the next page would be completely scrambled to any random characters that the printer could produce!

OK, before you see the reason, bets are being taken on the final cause and solution.

As it only ever occurred after a Form Feed operation, the tote software was checked first. Nope - even a simple custom diagnostic program could reproduce the problem. (Webmaster's note: Oh dear - Rob has compelled me yet again to sing my accord! Any minicomputer hardware technologist at the time, worth his salt, was very well acquainted with the architecture of the machine. It was a common requirement of the fault finding process to be able to write short machine code diagnostics which were loaded into memory using the console and executed to provide information on a particular problem.)

Old reliable Tektronix 'scope to the rescue. Fault finding in the printer logic revealed that when it was doing a Form Feed, AND when the page drive mechanism got up to full speed after a prior half-empty page, the servo paper drive logic with speed detection and feedback loop would go into oscillation (at about 200kHz, from memory), superimposing a massive high-frequency signal onto the D.C. drive voltage to the paper-drive motor. Unfortunately, the wiring from the control logic to the motor was held in the same wiring loom that carried data from the data socket at the back of the printer to the printer buffer memory. The printer had a 1-line buffer that would be accepting the next line of print from the computer as it was printing the current line, and so Bingo! .... When the servo paper drive system went into oscillation, the radiation into the data logic wires scrambled the data for the next line, which was of course the first line on the next page.

When the printer was new (and tested by DEC), there was no slack in the motor drive belt or bearings etc., and the logic kept tight control over the speed of the paper movement as it followed a smooth ramp up in speed until it (maybe) hit full speed, then a smooth ramp down in speed, leaving the paper at just the right spot to start the next page's printing. Beautiful when it was new. But as the printer aged and some mechanical slack came into the system, if the paper drive got to full speed, the feedback would try to keep it 'idling' along at the same speed, which set up the scene for oscillations when the control was designed to be too 'tight'.
(Webmaster's note: Yes I know, I know, why don't I just let Rob tell his story? Well he introduces so many pertinent observations of a whole field of work, computer component level repair, that no longer exists, due to the vast majority of machines these days being throw away replaceable items. Additionally the not so technical readers, will not be aware of the significance of writing which presumes a technical readership. Having justified my continuous interruptions, for the not so technical readers, this is an interesting fault. An obscure circumstance burst of electromagnetic radiation, inducing interference in the neighbouring data wires, due to a hunting closed loop servo system as a result of mechanical slack, caused by time related wear, is not the first thing that comes to mind when considering causes of such a fault. Consequently this has the earmark of a challenging fault.)

The fix:-
I determined that as the paper movement had to follow only a smooth ramp up and down in speed, over a period of 1 to 2 seconds, the feedback loop (which worked well) didn't need to have a frequency response of 200kHz. So I simply lifted a wire connection in the feedback signal, inserted a modest value resistor (probably 100 ohms, for example) in series, then put a small capacitor (say 0.1 microF) after the resistor, to earth - the simplest low-pass filter you can have. Bingo again! ... The printer still did its Form Feeds reliably, but no more oscillations under any circumstances, and hence no more scrambling of printed data. (Webmaster's Note: I just can't help myself, it just strikes such an accord with me! I love Rob's solution. There is an acronym, that I have heard in multiple fields of engineering KISS: "Keep it simple stupid". This is a simple but effective solution and for that reason I think it is the best. )

I tidied up the modification, wrote up the problem, its cause, and the field change I had done, and sent it all to DEC - whom I hope took action to modify their design and retrofit any change to existing printers. I had to put the same change into the second Harold Park printer and the 2 for Wentworth Park.

It was fortunate that the problem showed itself before the systems went live, as our only record of the betting details, totals and dividends that the system produced were the printouts after each race, on the 2 on-course system line printers. Remember - no discs in those days.

David Hamilton, who was the ATL NSW operations manager at the time the PDP8 system was introduced, also remembers the introduction of the PDP8 system in his tote memoirs in the Memories of an Ops Manager and Harold Park chapter.

Information and Images from Max Burnet ex CEO Digital Equipment Corporation Australia

On hearing that a web page of the Automatic Totalisators Limited's, Harold Park PDP8 system was being developed, Max contributed the following information with two very rare images:

In 2001 I was given two items by Bill Johnson of Stockton for the BACK museum collection. They are still safely on show at my house. I enclose a pic of each of them.
Max mentions the BACK museum which is a wonderful museum belonging to BACK Pty Ltd (Burnet Antique Computer Knowhow)

Rob Stone working on the PDP8 based totalisator at Harold Park The PDP8 Interface from Harold Park
Photo by Max Burnet and Peter Watt:

The front panel was made by ATL and provided information and control for the dual PDP-8 configuration.The two computers were simply called A and B. Either one could be the master. The panel used the same colour and style as the PDP-8 front console..

Rob Stone, who wrote the previous article above, added the following comment about Max's PDP8 Interface image:
Right on the money, showing the A and B computer output selection buttons and other indicators, as mentioned in our correspondence. And that Interface panel & cabinet can be seen right next to the 2 PDP-8s in the Duplex photo. (Webmaster's note: shown above titled Rob Stone with Duplex PDP8 system at Harold Park 1970)

A box full of PDP8 spare modules Wooden Box of PDP8 Spare modules for rapid repair
Photo by Max Burnet and Peter Watt:

The wooden box held a set of spare electronic DEC modules as used in the PDP-8's. Bill said he had the half an hour between the races to find and fix a fault. In those days DEC provided the customer with a recommended list of spare parts to have on hand.

The bright and colourful module handles in the above photo all had a purpose in life...
The purple handles indicated the module comprised Integrated circuits and were used for the PDP-8/I computers.
The red handles indicated the module comprised transistor based logic and were used for the interfacing equipment.
The white handles indicated the module comprised passive components such as wiring connections, lamp drivers etc
The green handles indicated the module was used to support the core memory of the computers. They had very tricky analog/digital circuitry that could make a grown man cry!
The orange handles indicated the module comprised analog circuitry.
At the bottom right of the photo is an extender board. A suspected failing module could be mounted in this extender, and examined with afore-mentioned oscilloscope. (Webmaster's note: So much rings an accord with me. Max has pointed out the extender board. Having spent so long in repairing electronic equipment and in particular DEC minicomputers these extenders played an essential role in the work I performed. Very few faults could be identified statically, so the board had to powered up and operating to identify the fault. This means it had to be on one of these extenders, so the faulty board sits proud from all the other boards, to expose the components to be able to attach the aforementioned oscilloscope, as Max puts it, to pertinent nodes in the circuitry with a probe. The only difference with my experience is that this is a single height extender board, meaning there is only one backplane connector. As I worked with the PDP11 computers, most of the PCBs (Printed Circuit Boards) I worked with, were hex height boards, meaning there were 6 of these connectors in a row on the one board and hence the extender as well. I notice that in the left half of this box the boards are all dual height which means it takes two extenders like the one in the image to extend these boards. You can see that in the two left hand columns of handles, the left hand handle is on the same circuit board as the right hand handle. There were a few dual height boards in the PDP11s I worked on like the Bootstrap/Terminator boards and the Parity Controllers.)


button with horsesGo back to the index   button with horsesGo to the bottom of the page

William Johnson made the following comment about Max's wooden box: Lynne's father, my father in law made two of the boxes for the spare cards. Always carried between Harold Park and Wentworth Park. We cycled the cards through the computers to make sure they were always working. (Webmaster's note: There it goes again, ringing an accord with me! If you are fortunate enough to have spare modules, you have to have a system of ensuring they remain functional. This is called ensuring you have viable spares. It is no good leaving them unused for ages, then in a crisis, using one to replace a faulty module, only to find your spare has developed a fault in the elapsed time since it was last used.)

Max later added the following images and observations:

An image of a Teletype ASR33 terminal

An ASR33 Teletype on the left and a close up of the ASR33 Papertape Punch on the right


Photos by Max Burnet and Peter Watt:






An ASR33 terminal showing the Papertape Punch

(Webmaster's note: These images show an ASR33 terminal which were the mainstay terminal in the era of this computer room. Rob mentions the ASR-33 Teletypewriter in his article above, regarding Indicator chaos. This is the type of terminal on which the operator triggered the indicator problems. The blank papertape can be seen at the top where it comes off the reel in the right hand image and the punched tape can be seen below the punch. I can well remember using these terminals to write and store programs written for a Data General minicomputer in my student years. In the image above titled "Rob Stone with Duplex PDP8 system at Harold Park 1970", in the cabinet he is working on and the one to his right, immediately below his elbow are two black looking devices one in each rack, above the two PDP8 consoles. These are papertape readers that read the punched tape seen hanging from the right hand ASR33 image. (Max, apologies for the Data General Appello Non Grata, no disrespect intended. (For the non technical reader, Data General was a competitor of the Digital Equipment Corporation founded by a breakaway group from DEC!))) Max, on reading this comment about Data General, made the following comment:

Our aforesaid arch rival, Data General, started with integrated circuits, so gave DEC hell about needing a bus converter. As a result we often gave away the bus converter for free and buried it deep in the 6 foot cabinets!

(Webmaster's comment: I have taken Max's comment out of sequence and placed it here to connect the Data General reference. As a consequence the need for a bus converter is explained in Max's information following:)

A PDP8 Backplane The PDP8 Backplane - Photo by Max Burnet and Peter Watt:

When Rob Stone talks about re-wiring the PDP-8/I, this is the daunting wiring complexity that he faced. The photo shows the PDP8I backplane. Factory wiring was done in red. Field changes were usually done in yellow. (Webmaster's note: For the not so technical reader, the image above titled "The PDP8 Backplane" is a close up view of what Rob is working on in the prior image above titled "Rob Stone with Duplex PDP8 system at Harold Park 1970". As there is no yellow wiring on the backplane shown here, as Max points out, there has been no Field Changes performed on this backplane. Rob will be using yellow wire in the photo with him in it.)

The first PDP-8 that DEC made around 1965 was made of transistors and diodes.(These were the R for red modules). Over time it has become called the "straight" 8, or the "classic" 8.

In my DEC aust history DVD there is a list of straight 8's on page 13 and 14. It shows ATL had two of them, serial numbers 564 and 740. They were probably in the ATL :"research dept" or "development lab" By their serial numbers I would estimate they were bought around 1964. (It sounds like Bill Johnson gave one of these to the university when it reached end of life).

The PDP-8/I was made with integrated circuit ( M for mauve) modules about 1971. The 4 at Harold Park and Wentworth Park were PDP-8/Is.

There was a major discontinuity between the two which was not featured very much. The straight PDP-8 had an I/O bus that was 0 to -3 volts. The PDP-8/I had an I/O bus that was 0 to plus 5 volts. This meant a whole new generation of peripherals had to be developed for the 8/I. Or use a cumbersome bi-directional "bus converter".

That explains why the box of spare modules has both red and mauve modules in it.

Retirement of these PDP8s from Tote life

When one spends a lot of time with systems, one gets attached to them and often wonders what became of them. Bill Johnson wrote the following about the PDP8 Tote systems at Harold Park and Wentworth Park:
I bought the 4 PDP-8s from Harold Park and Wentworth Park. Eventually sold them to deserving technical persons. The first PDP-8, all transistor, from research I gave or sold to my nephew Max and it ended up outside the maths department at the University of New South Wales.

In the same email Bill wrote the following, which was pertinent to me as I too worked for ATL and AWA and I have a long standing connection with Australian Aviation and probably used the aircraft beacons mentioned, which from the mention of towers and the era were probably ADFs (Automatic Direction Finder). I can well remember AWA's significant involvement in Avionics:
My brother Jeff while programming at ATL was asked if he would go to Indonesia for the installation. There was a "discussion" relating to alterations in conditions with Indonesia so Jeff did not go. He had previously worked in Indonesia for AWA installing aircraft beacon towers and electronics.

Memories of this era from Neville Mitchell

I attended the DEC training course with Allen Lakeman in Crows Nest, with Bill Johnson and Ray Stone. (Webmaster's note: Ray is Rob Stone's brother.)

(Additionally I have included the following reference to Wentworth Park as this system followed shortly after the Harold Park system and is mentioned by Rob Stone above.)
I recall the problem Rob Stone had with one of the high speed printers at Wentworth park. He spent many hours analysing the fault that turned out to be the printer drum which consisted of two print wheels on a single spindle one of the print wheels had loosened and moved out of alignment thus printing the wrong characters.

George Jenkins was also involved with me on the Wentworth Park CCTV system. We had completed the CCTV installation and it was working satisfactorily, then one morning we discovered a 50 cps hum bar rising horizontally on every monitor. I was at a loss to know where the interference was coming from, I called George to come and assist. It turned out that over the weekend the electrical contractor MW Ellison had altered the power points in each monitor housing adding earth wire from the GPO to the actual housing. The City Council Inspector had issued an E notice requiring the monitor housing be earthed, unfortunately the old Ledger grandstands electrical wiring was leaking to earth this ground voltage was the cause of the hum bar. The added earth wire was totally unnecessary as the monitor housings were bolted to the steel grandstand structure. A quick trip around the housings with a step ladder and a pair of side cutters did the trick.

I don't think MW Ellison's electrician at WP would question the Electrical authority's direction to earth the monitors GPO to its steel housing even given the housing was bolted to the steel grandstand structure. I knew the MWE electrician very well he was a Dutchman ex POW in Germany during WW2, he knew more about the Tote cabling of Randwick, HP & WP tracks than ATL did. He could terminate large W/P cables onto those ATL open frame terminal frames as neatly as the Women in the factory. Frank was a excellent artist, he had a love of aircraft especially fighters, he could do a wonderful water colour painting of a dog fight with English and German planes so realistic. Frank lost his life, when a power pole at Randwick collapsed.

At that time the two inspectors that regularly did inspections of works carried out by the on-course electricians, were a Mr Dear and a Mr Love. (Truly!) They even had leather bound copies of SAA3000 the bible of electrical work standards. I had studied it back in the 1950's when at Tech. ATL did follow its directives when it came to power connected manufactures. Anyway one day Messrs Dear & Love turned up at Harold Park. We had just finished and were testing the new large Ledger indicator. They came into the indicator and looked around at the systems and the 100 or so lamp panels. They sighted the data cables terminal block coming from the computer room on the paddock side of the track, "What are those Green wires?" they asked, They are part of a set of five data connections that fed the indicator with its 2 of 5 code. "You can't have green wires as green is always a earth wire" they said and began to write up an E sheet. The reason they were insistent on us changing the green wires was that the Paddock computer room was on a separate Power Grid system to the Ledger. About this moment, Ron Hood turned up and somehow convinced the inspectors that it was lunch time and he invited them to dine with him at the local Harold Park Hotel. I never did see an E sheet, or for that matter, did I ever come across Messrs Dear and Love again!

Webmaster's Note: Ron Hood was my first Manager when I joined Automatic Totalisators. I thoroughly enjoyed working for him as he afforded me the time to do a lot of study relating to ATL products and their engineering. So long as I had my head in a manual, an engineering drawing, or a diagnostic listing, he was happy. I learnt a lot from Ron!

The Thing about Friction

Friction in the workplace can be counter-productive, however it can also be the companion of progress. Rob Stone and Neville Mitchell wrote to each other, observing friction incidents at work. I have presented it here as I too have experienced exactly the same thing they observe. I have been asked to consider, that in diligently documenting engineering work, I am eroding job security. Rob also mentions a type of technical problem I have encountered. Sometimes in multiple board electronic devices, the technical documentation for the board electronics can be impeccable however the documentation on how the boards interconnect can be sadly lacking. On the other hand some companies had perfect documentation throughout. Two such companies whose equipment I have had a lot to do with are the Ampex Corporation and the Digital Equipment Corporation. I can recall being very impressed with the Ampex manual set for one of their broadcast standard Videotape machines, possibly the AVR2, as they even provided notes on Op Amp (Operational Amplifier) Theory. Reading this was like having a refresher course if your Op Amp Theory was rusty.

Following is an extract from an email that Neville sent to Rob:
Alf was my manager when I first moved from production electrical inspection. He was an Estonian, trained in a Russian tractor factory's drawing office. I normally got on very well with him, when I returned from several overseas installations, I would be re-assigned to the drawing office. I had learned a lot about the old tote machines, which was good, but I wanted to design peripheral gear for the burgeoning PDP8 era. I clashed with Alf and Talis over engineering failures regarding notable voltage drop over 120 & 50 volt ticket machine power lines, for J8, J10 and J11. There is a lot of voltage drop with DC currents and race tracks are usually large places, with long power lines. And other long held old fashion methods were strictly held to, so I was the new Upstart, causing some dissension in the office.

Following is an extract from Rob's reply to Neville:
Talking about striking resistance when you see something that can be improved: When I was putting the tote systems together and testing them at Meadowbank, I would frequently have trouble finding where a particular signal (say XYZ-12) came from or went to, when it was on a different page of say a scanner (with perhaps 30 pages of circuitry). Some signals would have page refs in brackets after the signals if off-page. But when I started adding page refs to signals, after spending the time to find them, or adding explanatory notes to pages where needed, our good mate Ron took me to task, using the reasoning: "Rob, if you dot every 'i' and cross every 't', they'll be less dependent on us experienced guys for explanations, setting up the systems, and the training of the overseas system engineers!"
I still snuck in (with your drawing office) whatever clarifications I could, whenever I got the chance.

On the subject of lack in interconnect documentation, Neville added the following:
Rob brings up the point about documentation. In the PDP8 days I often wondered why there was no general schematic for the PDP8 computer assembly, as Rob said several senior engineers kept certain crucial interconnection details to themselves. I would look at all those ribbon cables in Harold Park and Wentworth park and wonder to myself how they got there,the same applied to the Victorian PDP34 systems.
Thinking back as we all know, there was never, that I discovered, a total schematic of a Julius electromechanical totalisator system. There was ample documentation for each component part but no interconnecting schematics.

Two extracts from ATL International Name in Totalisator Betting Systems

ATL electronic totalisator system is the pacemaker at Harold Park

Harold Park Paceway has been host to many great trotters including Cardigan Bay, who won a million dollars in Australasia and the United States, and Lucky Creed who won 23 successive events. Their performances will be talked about at Harold Park for as long as people remember the time Dan Patch broke the two minute barrier for a mile at Yonkers. And that will be forever.

Harold Park Paceway was the first racecourse in the Southern Hemisphere to install an Electronic Totalisator System.

ATL did the job, its tenth successful Electronic installation since Aqueduct. This year there will be 89 race meetings at Harold Park, 47 of them for trotters and 42 for greyhounds. All will attract huge crowds, for this racecourse is the most important venue of its kind in Australia.

The N.S.W. Trotting Club, the company controlling Harold Park, at the moment can boast of having the most modern Totalisator facilities anywhere in the trotting world.

I have included the second extract from the company document ATL International Name in Totalisator Betting Systems, as Rob Stone mentions being the installation engineer for Wentworth Park as well as Harold Park.

Main features of Electronic System

Twin computers combine on-course and off-course investments at Wentworth Park. Closed circuit television is used to transmit Odds, Results and Dividends information throughout the Course for both public and internal use.

As an added feature, the running of each race is videotaped and played back to the patrons on monitors 2 minutes after the greyhounds have crossed the finish line.

The Computer Room incorporates the TAB off-course and ATL control offices in a fully air-conditioned area which is located in the Paddock Totalisator House and overlooks the track.

The Electronic Totalisator System is capable of serving 128 Ticket Issuing Machines selling Win, Place and Quinella tickets in the range of 50 cents to $50.

High speed Line Printers record the information stored in the computers. This information is available for checking and for record purposes at any time.

Logging Teleprinters record all instructions given to the computers and type out data as specified by the program. Instructions not taken care of by the program are keyed into the Totalisator Control Console which serves as an input device.

Calculations of Odds and Dividends are made by the computer under program control. The Lamp Boxes in the Indicator Board are activated by the Board Control Unit which is part of the computer complex.

Five selling divisions equipped with type J11 single value Win, Place and Quinella Ticket Issuing Machines serve the betting needs of the public. Both types of machine are fast lightweight press button units designed to efficiently and speedily handle business at the selling windows.

A new grandstand with many special design features is envisaged in future plans for Wentworth Park. ATL shares with the Wentworth Park Trust and the National Coursing Association their enthusiastic anticipation of this plan becoming a reality, thus providing another facet to the modern facilities offered at this internationally-known greyhound race track.

Technical Documents from Dick Sterndale-Smith

On May 25 2015 Dick wrote:

These stories have got me thinking about that era, but most of my memories seem to have faded over time, not withstanding all the people that I was fortunate enough to work with along the way. I remember I made the front page of Tote Topics, sitting at the PDP8 console toggling in that bootstrap program to get the thing started. We did know that program off by heart.

One thing I have in my possession is the "Proceedings of the Decus-Australia May, 1971 Symposium", where George Klemmer and myself presented papers which I have attached for your info.

Lastly, the one thing I will never forget working at Harold Park was the Friday(?) night that Kerry Packer joined us at the track with a few of his mates. I was in the dinning room having dinner when the entourage arrived looking for seats. Not sure if they had a reservation or not, but besides Kerry the only other person I remember was Tony Greig, the cricketer. Of course after they had arrived, the word soon got back to the stewards that the famous man was here, and a laky was dispatched to invite him to the Stewards box. All that I overheard was KP politely declining the offer, and stating he preferred the company of his mates (who may not have been invited).

Following is major content from Dick's documents:

A REAL-TIME TOTALISATOR - SOFTWARE ANALYSIS
R.F. Sterndale-Smith
Automatic Totalisators Limited
Meadowbank. N.S.W. 2114

Abstract

A real-time totalisator operates under a duplex philosophy with all functions divided into either foreground or background tasks depending upon their priority or importance. Foreground and background concepts are reiterated and illustrated. The format and content of each transaction through the system are discussed together with the error detecting steps taken. Major and minor priorities of background tasks are defined as are the data representation and storage requirements of different betting types.

INTRODUCTION
The electronic totalisator is a real-time betting system providing for the selling and recording of bets on races, together with a cycled display of odds and the subsequent calculation of dividends for winning bets. The system operates continuously from the start of the first race and cycles race by race until the completion of the last race.

The totalisator program can be divided into a foreground interrupt service routine and a background Executive (EXEC) program. All functions are similarly divided into these two groups - foreground and background depending upon the priority or importance of the task.

FOREGROUND MODE
Each foreground service routine is associated with a peripheral. So, with the interrupt facility enabled, hardware flag settings immediately interrupt both processors, stalling the EXEC or job program in progress. Their position and state are stored with control being transferred to a supervisory routine. This routine polls all the device flags and transfers to the foreground routine unique to the device.

With the single interrupt level, all foreground tasks have a higher priority than background tasks and must not share routines with background tasks since no special re-entrant steps have been taken. Foreground programs have a positional priority based upon their place in the skip chain. Devices first in the chain are those with the highest priority (e.g. power low detection and scanners) or frequency of occurrence (e.g. the line printer).

It is a necessity in this real-time application that all input to the system be accomplished in the foreground mode. In particular keyboard input, buffered and left for processing by the background program, may be overwritten before the EXEC reaches it, if processing time is consumed by other foreground servicing. With the processing being done in the foreground and the echoing in the background, the problem of losing a character before echoing is still present. A stack is needed to store the characters prior to echoing them.

As mentioned all processing related to input is done in the foreground mode, so that this implies all device loops are associated with output peripherals.

BACKGROUND MODE
The EXEC consists of a main control loop and as many device loops as there are peripherals whose output operations will be overlapped with processing. Control moves cyclically around the device loops and only enters those which are not already occupied in data transfers. To this end, each device loop has its own busy indicator and an address pointer related to the position that the EXEC has reached in completing a task.

If a device loop is free when interrogated from the main control loop, the EXEC commences checking for jobs or tasks that are waiting. When a job indicator is found set, the EXEC releases control to that job. These indicators can be set from the foreground mode, or alternatively after background processing to signal the readiness of data to be outputted . Job indicators that are set, eventually result in an IOT instruction being issued; whereupon the busy indicator is set, the address pointer is updated and control is returned to the main control loop. After the device flag has been serviced (in the foreground mode) by the clearing of its flag, and clearing the device busy indicator, the device loop is once more free and the EXEC can continue in a similar fashion with the task until completion.

Whilst routines cannot be common to both foreground and background modes this does not preclude routines being shared between different device loops. Two conditions must be satisfied. Firstly the routines may not contain IOT instructions, since the EXEC could progress to other device loops where the routine might be called again for the loss of the first return address. Secondly, data pertinent to these routines cannot be stored in common storage areas.

COMPUTER SYNCHRONISATION
Both computers operate asynchronously in terms of their cycle times, but after checking all device loops i.e. each time the EXEC is transversed, both the computers must wait for each other before they step off once more. This degree of synchronization is accomplished by testing a single flag in each computer which is skipped on if both are set and again if both are cleared. The interface circuitry emits an audible and visible alarm for a lack of response from either computer.

LOGIC LOOP
In addition to the device-oriented loops, there exists a loop related to no device, but compatible in structure with the rest. It is termed the LOGIC loop because it maintains the structure or logic of the device loops, and is responsible for passing the foreground to the background, calculations which justifiably belong to the latter. This is accomplished by foreground routines changing indicators which belong to the LOGIC loop. All LOGIC loop tasks are those which exclusively involve processing and consequently its busy indicator will never be found set and is superfluous. Its pointer is still used though, so that the flow of information to other peripherals is not inhibited by the relatively long period spent in calculations. Some functions then are only completed after a number of passes through the EXEC, which is analogous to the operation of the device-oriented loops. After completion and calculation, another indicator change flags a device dependent loop to initiate the output of the resultant calculations.

TOTALISATOR CONTROL CONSOLE COMMANDS
The sequence of events during a meeting is controlled from the Totalisator Control Console (T.C.C.). Here commands such as STOP BETTING or COMPUTE DIVIDENDS are initiated, which execute as foreground tasks and pass control over to peripheral dependant jobs by the setting of job indicators as described under the Background Mode Section. All T.C.C. commands, which do not directly produce hard copy, are logged on the teletypes with the following information: race number, current time and date.

Most T.C.C. routines can be separated into three phases. The first is the validation phase where it is determined if the 6-bit byte presented at the interface is legal. The next phase, which is not always present, requires that the command pass a series of logical tests, such as not allowing START BETTING unless a field of runners has been entered. The final phase consists of the response or action. Upon failing any pre-requisite, the command is not attempted, rather a diagnostic is logged, together with an audible alarm being sounded.

MAJOR & MINOR PRIORITIES
Central to the whole tote program is the calculation and display of progressive odds and finally the calculation of dividends for the results of a race. Both tasks have a certain intrinsic level of urgency i.e. a major priority in that they cannot be stalled by earlier request upon themselves. These tasks are distinguished from others in that their output is capable of self-interruption. Hence if dividends have been computed for incorrect results, new dividends can be recomputed before the termination of the normal dividends printouts.

There is one exception to this priority status though and that is the RACE INCREMENT task. It is pressed once per race and involves moving current race data into previous race data areas and for the Doubles, previous race data into penultimate areas. Thus because of its singular importance, the printouts from this instruction are incapable of interruption. As a general rule, previous race data areas are only accessed by routines that compute dividends. Dividends are therefore only calculable after RACE INCREMENT and can be re-computed any time up until the next RACE INCREMENT in the case of a protest being upheld.

The minor priority is only associated with the calculation of odds and is a function of how it relates to other jobs which also want to re-calculate odds before a previous set have been fully utilised. This minor priority works on a "first come first served" basis with the proviso that further requests are not queued, instead they take advantage of a current set of figures. Then after the last odd has been posted, and only then will the next request be honoured with an updating and recalculation of odds.

The major priority jobs are of course capable of breaking this dependence, whereupon the interdependent task is started again from the beginning.

TICKET ISSUING MACHINE TRANSACTIONS
The data associated with each transaction from a Ticket Issuing Machine (T.I.M.) is presented through a scanner to the computer in four 6-bit bytes. The first data word has one of two formats depending if the bet involves a single runner or a combination of runners.
Single Runner Transaction:

Combination Runner Transaction:

The second data word consists of:
BYTE No.1 - bet type or pool codeBYTE No.1 - 1st leg runner codeBYTE No.3 - value code
BYTE No.2 - runner codeBYTE No.2 - 2nd leg runner codeBYTE No.4 - T.I.M. number

BYTES No.1 and No.2 are variable data dependent upon the transaction and are supplied from the T.I.M. BYTE No.4 is implicit in the current position of the scanner.

The above data must be processed by sorting firstly on its pools and runner combinations and secondly on its T.I.M. or scanner address. If betting is not open, a REJECT signal is returned to the T.I.M. If betting is in progress, then the transaction must be validated to insure that no transmission errors have been made by checking data bytes Nos. 1 to 3. This data is now ready to be sorted on its pool type in Win, Place, Quinella, Double or Forecast etc., and the pool processing branches continue checking with the following elementary checks being typical:

After adding the value of the bet to both the runner total and T.I.M. totals, a CONFIRM signal is sent to the T.I.M. via the scanner. The ticket is now physically printed and the scanner looks to grant service to any other requesting T.I.M.

REJECT signals belong to one of two classes, with both inhibiting the printing of a ticket and releasing the keyed information.
A REJECT No.1 is used if betting is off or for a bet on a non-runner.
A REJECT No.2 is used for an illegal data byte.

Invalid data, all four data bytes together with the scanner number is stored in a cyclic buffer, so that faulty transmission or encoding of data can be located and rectified.

DATA STORAGE
All runner totals are held as double-precision integers. The total being an integral multiple of a unit or minimum bet. By storing all information on runner combinations, a progressive total of money bet on each runner or combination is maintained and at the end of betting, these are the final totals. The size of data storage areas is known in advance and relates to the maximum number of runners that the tote equipment is designed to accommodate. For PDP-8 systems, a field of 12 runners is preferred.

WIN & PLACE
Win and Place are two distinct pools, with one dividend usually being paid in the win pool and two or three in the Place Pool depending upon the number of runners. These totals are stored in vector form. 1-origin index referencing is used and since there are two words per runner, the total length of the vector is 2r, where r is the maximum number of runners in the field. 1-origin indices were chosen to preserve the correspondence between runner numbers and vector elements. Hence a bet on horse number i, i.e. W[i] or P[i] is stored at the address starting at, B + 2(i - 1), where B is the base or starting address of the vector.

QUINELLA
Quinella bets correspond to nominating the first two runners past the post in any order so that 1-2 bet pays a dividend if either one took first place and two second or vice versa. Totals here are again stored as a vector instead of as a matrix which would be more than half sparse. This amounts to considerable core saving when such storage areas may be repeated up to ten times in a system program. The total money wagered on Q[i,j] is stored in the double precision address starting at, B + r(r - 1) - (r-i+1)(r-i) + 2(j-i-1).

DOUBLE
Double bets correspond to selecting the winner in each of two races and are stored as a 2-dimensional matrix D[1:r,1:r] with the rows representing first leg runners and the columns second leg runners. Total storage required is 2r², while element D[i,j] is stored in the address starting at, B + 2[r(i-1) + (j-1)].

FORECAST
Forecast betting corresponds to nominating the first two runners, in one particular race past the post in their correct order. Its storage requirements are analogous to the Doubles except that the leading diagonal always contains r zero elements. This is because the combinations F[i,i], i=1 ,..., r are invalid.

T.I.M. SALES
Each sale of a ticket is also recorded against the machine from which it originated i.e. total sales from a machine are recorded and can be accounted against the cash in hand at each selling window. T.I.M. totals are stored similarly to runner totals as double-precision integers in core using self-indexing with a unique address being computed for each machine by concatenating the scanner number (derived from the device number) with the T.I.M. address on the scanner.

SALES PRINTOUTS
At any time, a PRINT TOTALS may be requested whereupon, W[1:r], P[1:r], Q[1:r((r-1)/2)] etc., are buffered with the interrupt disabled. The printout form the buffered area follows on line printers together with odds and grand totals in each pool. If betting has ceased T.I.M. totals which are now static may be included since their total will agree with the sum of all the pool grand totals. T.I.M. totals are ordered in core by scanner sequence, while they are printed in window number sequence. The T.I.M. addresses to the windows are not allocated sequentially for practical reasons. Hence to be able to print in window number sequence, a vector with two words per entry is needed. The first word represents the selling window number and the last word, the scanner address, acts as a pointer to the T.I.M. total.

...

CONCLUSION
The totalisator program relies on a foreground/background capability, which enables the central processor to be used for more than one task simultaneously. This construction could easily form the basis of many other multiple device systems.

ACKNOWLEDGEMENT
The Author is indebted to Mr. G. Klemmer for numerous discussions which have contributed to the present state of this real-time totalisator. Colleagues both past and present have also assisted while particular mention is due to Messrs. F.G. Rolls and M.W. Nimmo.

...

A REAL-TIME TOTALISATOR - HARDWARE DESCRIPTION
G. Klemmer
Automatic Totalisators LImited Meadowbank. N.S.W.

ABSTRACT

A totalisator system for Race Tracks is described, which is based on PDP-8 computer. To provide high reliability and certainty of results, two PDP-8 computers are used in twin configuration, where the input goes into both computers and is processed identically. The system also accepts off course information from T.A.B., calculates and displays odds and final dividends.

A totalisator system usually comprises a multiplicity of terminals or ticket issuing machines (T.I.M.s) 100-600 in number, scattered around a race track which print and issue betting tickets. The T.I.M.s are connected to central recording equipment which registers every transaction and accumulates totals of money bet on each runner or combination. Usually it also has a public display board which shows the state of betting and final dividends payable.

Up to the early 1960-s such systems throughout the world had been electromechanical. In 1966 A.T.L. installed a large system in U.S.A. using large data processing machines. The system was very expensive. It was then realised that the same result could be achieved by using inexpensive mini-computers and all subsequent electronic totalisator systems installed by the company have been using PDP-8 family computers.

Figure 1

The tasks that the computer has to perform in the totalisator system are rather simple. Nevertheless, it is a true real time system where downtime cannot be tolerated, and it is not possible to switch to manual control if a catastrophic failure of the system occurs. For this reason the system uses two computers in twin configuration. This means both computers have the same status and are performing the same tasks. The input from the T.I.M.s goes into both computers and is identically processed. Should one of the computers fail , the other will continue operating without system degradation.

In a typical totalisator system following computer equipment is used:

  1. 2 X PDP-8 each with
  2. 16K memory
  3. ASR teletype
  4. HS Reader Punch
  5. Line Printer

Of the above options, item 4) is required only for convenience of rapid program loading. Item 5) is used for printing out all relevant race information during a short time interval of 3 minutes or less, between "Stop Betting" and "Start Betting" on the next race. This information is used for record purposes only, but is in most cases a government requirement.

The rest of the interface is constructed from DEC R and W series circuit modules. A block diagram of the entire system is shown on Fig . 1. Each T.I.M. scanner interfaces 64 ticket issuing machines. It tests each T.I.M. in turn for presence of a BID signal. When a BID signal is found, a SCAN signal is sent to corresponding T,I.M, which in turn causes the data from T.I.M, to be transmitted to scanner data register and the scanner to generate a service request signal to the computers. The computers then read in the data and start processing the bet. After the bet has been processed, the computers send either a CONFIRM or REJECT signal to the scanner. If the signals from both computers are in agreement, a corresponding signal is sent to the T,I,M,, which in turn will drop off its BID signal. Fig, 2 shows the signal connections of a typical T.I.M..

Figure 2

The display buffer provides means for storage of information to be displayed one field (up to 6 digits ) at a time. In addition to information, the field address is also stored in the buffer and decoded to select the field to be displayed. The display buffer is connected to output of either one or the other of computers by means of a manual switch.

The operators console provides the totalisator operator with a means of entering information into computers which is necessary to control the system during betting. Some pushbuttons on the console generate coded messages which cause the computers to take necessary action whereas others condition registers which establish lists of valid runners and results of the race. The commands entered via operators console (T.C.C.) as well as final dividends computed by the computers are logged on both ASR33-s. This provides a visual check that both computers are in fact in agreement. The clock signal is used to initiate display cycles and to keep the time of day which appears on all printouts.

The special Teletype is used on Australian race tracks for entering manually Totalisator Agency Board figures for the race. At present these totals are transmitted from TAB office to the race track by phone. It is hoped that in the future TAB will be able to transmit their figures directly into the computers via data link. For reliability reasons the system uses redundant self-checking codes for T.I.M. data and public displays. There are also checks inbuilt into the system to ensure that both computers are in fact operating correctly. One of these, as explained earlier, is the requirement that identical signals from both computers are required to confirm a bet. There is also a special circuit provided in interface equipment which synchronizes the computers in the main program loop. (Fig. 3). Following seven instructions accomplish this task.

FRED,SET FLAG
SKIP ON AB SET
TRY AGAIN
CLEAR FLAG
TEST FOR ̅A̅ ̅B̅
JMP INIT
TRY AGAIN

Figure 3

Every time the computers exit the check program the R303 is retriggered. Should one of the computers fail reaching the check program the one shot will time out and sound an alarm.

Over 15 systems as described above have been installed on race tracks throughout the World since 1968. They have functioned reliably in adverse conditions for the benefit and pleasure of racegoers.


Fancy Line


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