KBK update for Wednesday, 13th October

Some time ago, I came across an advertisement in Computerworld from May 1976 for ITW’s “series 54 Superswitch II” “solid-state” keyswitches. Without any illustration, and with the ambiguity of the term “keyswitch” it was not entirely clear what Series 54 was, but it seemed fairly likely to be one of ITW’s ferrite core keyboard switch types.

Chyros recently uploaded a video reviewing an HP 264x keyboard. Although the errors in the video reached an egregious level (including the laughable notion that Licon had no idea what they were doing when they invented the ferrite core switches), a comment in the video about the Reset Terminal switch—made by Cherry and resembling M61-0100 in Style B form—being double action was an interesting lead to follow. This switch is listed in the service manuals as single pole; tracing the HP part number led to a Cherry part of M51-0108, again indicated to be single pole momentary. (This part was for sale on eBay along with various other HP spares including some ferrite core switches, so soon we should know what that specific model is; in the eBay listing the Cherry switches were concealed within brown paper bags.)

Proof that at least one HP part number could be traced to a manufacturer part number led to more digging, which turned up some actual ITW part numbers from the HP 264x systems: 54-0013, 54-0202 and 54-0203. The last two have cruciform mounts that presumably accept Cherry keycaps. These three types should all be Series 54 based on the part numbers, and that places them within the Superswitch II series. This appears to confirm that the keyboard and switch series were entirely separate, with Series 54 being a series of switches used in Series 555 keyboards. (There were two switch designs patented at the same type, and it’s not known whether both are the same series.)

Quite what the recently-discovered Super Switch switches are remains a mystery, as those appear to be the correct dimensions for Series 54.

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