Reorganizing my desk - more exact the piles below - I once again came across this mystery front-panel. I can't remember what it was from nor who owns the ||/ logo present on chips and board(*1).

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Front Side

Of the switches all are toggle, except in the top row the two left and rightmost are momentary. So while the ones in the top row are of different size (maybe according to function) and grouped, they still differ within the first group.

The lower row are 24 toggle switches and Lamps. Don't get confused by the missing 9th lamp (from the right). With 24 toggle switches in the bottom row, it may be either have been a 12 bit machine (12 bit address/12 bit data), or an 8 bit with 16 bit address.

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Back Side

The top left writing is CSL CONT while the number on the top right is 11001481-D. The two metal braces at the metal frame are numbered 15000751.Speaking of metal, the bolts and nuts used seem to be imperial, so it's either a US or UK product, as any other place would have used metric.

Each of the three IC, labelled IO/7, seem to encode the switches (maybe 12 bit wide,as 8 from below and 3-4 from above) and controlling 8 lamps. They all carry the same production number 91130072.

I would assume their part number system being based on 8 digit numbers (*2), possibly structured, possibly with a 2+ digit type code (left justified) with the remaining counting parts.

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There's also a paper sticker with what appears to be a serial number:

5122 271 03041
SERIAL 400580

*1 -I'm pretty sure I will feel like a real idiot as soon as someone points out that logo.

*2 - 8 being a nice length for such, often pointing to a /370ish system using BCD (4 byte key length).

  • No clue from the large ICs on the board?
    – chthon
    Jan 29 at 14:23
  • @chthon Not really, beside them being really early ones. For sure no later standard devices. They seem to be made by (or for) the same company that made the PCB. Added detail pics.
    – Raffzahn
    Jan 29 at 15:13
  • 1
    The bottom row of switches seems to be grouped in 15 and 8. Could be a PDP-8 clone (I'm thinking with its 15-bit addressing). The eight switches might be the usual front-panel ones: Deposit, Load, Cont, single stepping, etc. etc. Does that sound plausible to you? Jan 30 at 17:34
  • 1
    It would be useful information, if you can include it, to know which of these switches are momentary contact switches. And, if you are sure this circuit board even comes from a computer, and not from, say, an alarm system or something. Jan 30 at 17:34
  • 1
    Also, I did find this exchange, but it unfortunately doesn't add any new information. forum.6502.org/viewtopic.php?f=1&t=3183&view=next
    – Geo...
    Jan 30 at 18:00

1 Answer 1


Four-Phase Systems

I worked with others who programmed Four-Phase computers. I really can't add more. I simply remembered the logo.

This image appears to show a similar, if not identical front panel.

Four-Phase Computer

(Image source)

  • 4
    This is awesome. Thank you so much. This panel bugged me the better part of two decades. Now I need a detailed picture of the front screen to make it look like it should. Plus ofc, all I can get on that system. New Target acquired :))
    – Raffzahn
    Feb 1 at 2:49
  • 1
    Oh, and yes, as predicted, I feel totally dumb now. Of course I know the Four-Phase systems and their logo.
    – Raffzahn
    Feb 1 at 3:24
  • So the logo is not "||/" but rather "IV"?
    – Theodore
    Feb 2 at 14:46
  • 1
    @Theodore - A stylized Roman numeral "IV" with the "V" slanted and separated at the bottom thus providing a distinctive (and in my case, memorable) appearance.
    – Rick Smith
    Feb 2 at 14:57
  • Oh snap. I just bumped into this logo in a random youtube video about Four-Phase Systems and was super excited to come back and answer this question. Only to be ninja'd 3 months ago... sigh
    – Geo...
    May 4 at 23:15

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