Controls Research BI-PAC
Overview
Controls Research BI-PAC is a mechanical switch type whose switch contacts are a pair of concentric coil springs. The wider outer spring has the top end formed into a horizontal bar, and as it is pressed down by the plunger, it makes contact with the top of the inner spring. The springs form the solder terminals. Overtravel is achieved when the inner spring is also compressed.
The switches are formed into blocks that are almost identical in layout to Key Tronic and Maxi-Switch switches. The switch blocks and inner workings are illustrated in Electronic Design magazine in 1972 [ED1972-FOK], under the name “Bi-Pac”.
US patent 3773996 “Pushbutton switch with coil spring contacts” filed in 1971 covers the design, and describes a means for it to provide tactile (“snap-action”) feedback; British patent 1345831 was also filed, in May 1972.
The series name is spelt “Bi-pac”, “Bi-Pac” or “BI-PAC” depending on the source. In Electronic Design magazine in 1972, “BI-PAC” is used in the body text, and “Bi-Pac” in the image caption. Official advertisements and the HAL DKB-2010 manual use “BI-PAC”, while the 1971 Electronic Design written advertisement and 1972 Electronics article use “Bi-pac”.
Examples
There are only two confirmed examples in full-size keyboards:
- Micro Computer Machines MCM/70 keyboard, assembled in Mexico in 1974, and labelled “N10046 REV AP1” and “B30041-1 REV AP1”.
- The HAL DKB-2010 manual, November 1978 reprinting, lists switches S101–S153 as ‘Controls Research “BI-PAC” Keyswitch’ (such a keyboard is in Engicoder’s possession, but the switches are not discrete but rather in the expected blocks) while the keyboard diagram depicts Stackpole Lo-Pro switches as per Jacob Alexander’s example
In [ED1972-FOK] a complete calculator keypad is shown, that uses Bi-Pac switches. A very similar CRC keypad was used in the Summit 3114, with the main difference being a slightly different key arrangement.
Two stock BI-PAC keyboard models are depicted in advertisments listed under Documentation below.
Documentation
- Bi-pac advertisement, Electronic Design, November 25 1971, page 91 (scanned by Bitsavers)
- ANSI keyboard advertisement, Electronic Design, August 3 1972, page 75 (scanned by Bitsavers)
- ASR-33 keyboard advertisement, Electronics, February 15 1973, page 172 (scanned by or for WorldRadioHistory.Com)
- Keyboard sells in $50 range, Electronics, September 11, 1972, page 173 (scanned by or for WorldRadioHistory.Com)