How to use Virtual ERNIE

Virtual E.R.N.I.E

Virtual ERNIE is a working simulation of the original ERNIE 1 to allow you to learn how it worked. Please note that the random numbers generated by this simulation are not genuinely random but created using the pseudorandom calculations of your computer (so don't go using the for any real draws!).

Virtual ERNIE - ©2019

Moving around and clicking

To view different sections of Virtual ERNIE, simply click and drag the webpage or if you prefer, use the scroll bars. To view closer or to get a larger overview, you can use the mouse wheel (if you have one) to zoom in and out or for those on a touch screen device, simply pinch zoom as you would normally. A control panel is available in the top left which also has buttons which enable changing of the zoom level.

The control panel also has switches which 1) Rotate Virtual ERNIE so you can view the back, 2) Show/Hide the console and 3) Show a "portal" to the remote SPU teleprinters (Note: a space/time portal was not part of the original design!)

You should find blue help buttons dotted around which will give more information on the various sections.

Controls that can be changed are denoted by the cursor changing to the standard webpage hand icon. To change a switch (or key as they were known at the GPO), either click on the top half of the switch to move it upwards or the lower half to switch down. Note that some switches are sprung so they will return to their original position after setting.

The console

The console is the large table front and centre! It houses the two main teleprinters used to output the numbers generated by ERNIE along with the main controls.

The left-hand set of controls on the console house the warning and error lights plus the teleprinter controls, reset and alarm keys. The oscilloscope mounted on the right side of this panel displays the output to the teleprinters. More detail on these controls are available by clicking the blue help button "ERNIE Console" which is just to the bottom-right of the console on screen.

The right-hand panel on the console has a set of warning lights which are notification from each of the remote spur teleprinter stations along with the start, pause and emergency stop keys.

To start ERNIE running, simply click on the lower half of the start switch on the right-hand panel of the console. If you have sound, you should hear the teleprinter start up and the master printer oscilloscope will begin displaying the output. To view what is being printed, try moving to the printer on the far left of the console table. There is a blue zoom button situated there which will try to zoom you in to full zoom and get you somewhere near the teleprinter (although this function may vary on different computers/browsers). [Note: Some browsers appear to be better than others at showing such small rotated text and this may appear somewhat blurred). If you are struggling to see what is on the teleprinter, there is a monitor teleprinter which you can use to see the output (which is not rotated). Click the switch marked "Start Monitor Teleprinter" on the console to show it.

The output will be a series of "randomly" generated nine-digit premium bond numbers along with an incrementing serial number to show the order in which they were printed (higher value prizes are allocated first!).

To stop Virtual ERNIE, click the Pause key down (which will stop after the next number has completed) and then you can switch the Start key back up to the Off position and un-pause. Pressing the Emergency Stop button will trip the power breakers and you'll see the lights all go out. (Note: If you do this, you'll either need to reset the page or find the circuit breakers at the bottom of the rear second rack in to restart).

On the front of the console, you'll find two drawers. The left hand one contains a link to a YouTube video called "The Importance of Being E.R.N.I.E" which is an instructional film created for the General Post Office in 1964. The right-hand drawer contains a series of Post Office Engineering Department research reports which contain lots of extra information. Click or hover on any one to view closer up - the full PDF for each can be downloaded for you to view offline. These PDFs are © BT Heritage and are also available on the BT Archives website along with many photos (search for ERNIE).

The front rack

ERNIE is housed in five, double sided racks which during the draws were kept closed and locked to prevent tampering. You can open the rack doors by clicking on the door handles.

The front racks are numbered from five down to one from left to right with the contents as follows:

5. Teleprinter selector circuitry and power supplies.
4. Element scanner, one-only alarm and the master control circuitry
3. Counters, Combiners, core stores and the master/character distributor printed circuit boards. (ERNIE 1 was the Post Office's first large-scale use fo transistors and printed circuit board techniques).
2. Random noise generators and binary triggers. (This is the part that actually generates the randomness)
1. Power Supplies

For more detailed information, see the blue help buttons against each rack or start reading into the research reports in the right-hand drawer of the console.

A few things to try out:

1. Find out what happens if you switch off a power supply (to simulate a failure).
Try switching off psu number 7 (the small on/off switch in the centre of the PSU). Firstly, the alarm will go off (as ERNIE has lost power to some of his random number generators) so you can stop this by pressing the ALARM key on the console up to Restore or set the Alarm Cut-Out key down to disable it. ERNIE was built with numerous spare parts ready built in so if a fault occurred, a replacement component could be switched in as quickly as possible. Each power supply has a cable connecting it to the rest of ERNIE so to replace this "faulty" power supply, we can simply switch the cable to the PSU marked SPARE just below it (click on the end of the cable connected to the PSU and it should swap to the nearest spare). Switch the spare on and you're good to go!

2. What happens if a random number generator fails?
On rack 2 (the random noise generators) is a blue button with a spanner/wrench icon. This enables you to disable one or more of the RNGs to show what would happen. Due to the way ERNIE was wired, with two separate random generators feeding each digit of the bond number being generated, ERNIE could continue to work even with one of the RNGs failed completely! Set a fault on one of the RNGs using the spanner/wrench button - you should see that the "One random generator fail" warning light will display on the console to warn the operator and the cold-cathode tube on the related binary trigger will fire and light up, showing the number of random pulses being generated has fallen below a set value. At this point, ERNIE can continue to generate random numbers without any problems! If you make a second RNG fail though, this could potentially mean both RNGs feeding a single digit could have failed so ERNIE will automatically pause and give the "Two random generator fail" warning until the RNG has been swapped to a spare or the fault fixed. (Click the spanner/wrench icon again to fix the problem).

3. What would happen if one of the teleprinters jammed?
On the Virtual ERNIE control panel at the top left of the screen is a switch marked Hide/Show SPU. Set it down to "Show SPU" and you should see a view of the remote file teleprinters. As ERNIE generates numbers, they are automatically routed to one of the eleven sets of file teleprinters so if you have ERNIE running, you should start to see some of the bond numbers being printed. If a fault occurred, for example a paper jam, the SPU station operator could notify the main console by pressing the Call key down (it's the left of the two green switches on the grey box above the right hand teleprinter). This will light up the relevant warning light on ERNIE's main console. Note that the number shown against the warning light is not the denomination - it's the internal phone number of that SPU station! The main operator, seeing the notification, would then set the Pause key down. Setting pause not only stops ERNIE generating any new numbers, but also sets a light on top of all of the SPU boxes to show we have a paused condition. The right-hand telephone was set to be on the internal phone network and so could be used to call up the station at fault to find what the issue was and to help resolve it. Once the problem was fixed, the SPU station can reset their call key back and ERNIE can resume printing.