Mechanical Enterprises Sabrecoil
Sabrecoil is a switch grid (array) system from Mechanical Enterprises: all the switches are formed from a single plastic frame, similar in general idea to Hi-Tek High Profile and Stackpole’s KS-200 and KS-200E. Standard grid sizes of 58-position, 64-position, 16-position and 20-position were advertised, but all full-size examples discovered so far are based on a 60-position array. The heyday for Sabrecoil seems to have been 1979–1980, based on current discoveries.
No formal specifications for Sabrecoil are yet obtained. The 1982 advertisement indicates that in testing it had reached over five million cycles, with contact bounce still below 15 ms at this point. Although membrane keyboards can have bounce times as long as 20 ms (such as Alps KFNR Series), mechanical switches are typically rated at 5 ms or less. One of the selling points of Sabrecoil is that the switch contacts use silver plate instead of gold, for a lower cost (at 50¢ per station in 1982), bringing with it a longer bounce time. Sabrecoil was introduced in the era of microprocessor-driven keyboards, where the longer bounce time could be handled more readily (such as directly within the operating system), as a trade-off for the reduced cost.
Sabrecoil keyboards are not widely encountered. A few examples are now known:
- Acorn used a 60-key Sabrecoil array for the first four versions of the Acorn Atom (Issues 1 through 4). They dropped Sabrecoil with Issue 5 of the Atom (the final version), changing over to Futaba ML discrete mechanical switches in the process. Acorn would continue with discrete mechanical switches for some years.
- AMD specified Sabrecoil for their evaluation kit for the AmZ8000 CPU: a key array matching the design of that used in the Atom (switch frame and the distinctive keycaps) can be seen in their advertisements (see Documentation below). This keyboard appears to be based on the same 60-key array as used by the Acorn Atom, but with the three double-width keys there are only 57 keys in total.
- Powertran’s PSI Comp 80 kit-built computer use two arrays: a 56-key main array and a separate 16-key numeric keypad. The main array is also a 60-position unit, this time with four key stations unpopulated. These could be seen clearly on an eBay advertisement that has since been erased by eBay. It can also be seen in an advertisment in Computing Today from June 1979.
All literature scanned by Bitsavers unless otherwise noted.
- Advanced Micro Computers evaluation board advertisement, Computer Design, August 1979, page 182
- Advanced Micro Devices Am96-4016 advertisement, Computer Design, March 1980, page 56
- Modular keyboard advertisement, Computer Design, August 1980, page 208
- Sabrecoil advertisement, Electronic Design, 1982, collected by Marcin Wichary
- Powertran PSI Comp 80 advertisement, Computing Today, June 1979, collected by Flax Cottage
- MEI Sabrecoil on the Deskthority wiki, for prior notes and illustrations