Clare-Pendar Series S840
Clare-Pendar Series S840 is a comparatively rare mechanical keyswitch range. The series was identified from an eBay listing for NASA surplus part, with NSN 5930-01-089-6772. This NSN indicates S84010, but the type in question appears to be S84010 K2.
No documentation has been found for this series, with the exception of modification codes, such as K2 for the crenellated mod.
The age of the series is not known. The original keyboards for the Texas Instruments Silent 700 models ASR 732, ASR 733, KSR 732 and KSR 733 terminals all use S840 switches. The ASR/KSR 732/733 brochure is from September 1973, and the oldest keyboard found to date: 720731-K1 listed on eBay (TI part 959326-1) has a Texas Instruments TMS 5000 single-chip encoder from week 4 of 1973. The brochure shows the uppercase-only 56-key keyboards; the Computer History Museum has a Silent 700 ASR with the 64-key full ASCII keyboard, as shown in the eBay listing. (A 1976 56SW5-2 indicates that Texas Instruments later sourced these keyboards from Micro Switch.) There was also a Baudot keyboard option.
pyrelink at Deskthority obtained another 720731-K1, this time with two keys—Break and Here Is—left of Paper Advance, instead of a single Reset key (the unused positions on the right appear to be where he had already removed keys). This is still marked with Texas Instruments part number 959326-1, this time revision E, with a slightly more recently-made encoder (week 44 1973).
pyrelink’s and snuci’s examples both featured gold crosspoint contacts,with triangular prisms like in German-made Cherry M7, M8 and M9 switches. By comparison, the only examined illuminated type had simple pressed metal contacts without dedicated prisms.
- Clare-Pendar Series S840 on the Deskthority wiki for prior notes and illustrations