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Bunker Ramo

The Bunker-Ramo Corporation, later known as “Bunker Ramo” (without the hyphen) was an American electronics and computer systems manufacturer.


Bunker Ramo manufactured a keyboard described as the “Admin Keyboard”. Two examples are known, a German-layout “ADMIN KEYBRD” and a Yugoslavian-layout “BCS-90 ADMIN KEYBOARD”. Both of these keyboards use Micro Switch SD switches, with keystem type “K”. The description of stem “K” is given only as “special blade”; it is a non-standard option which may be a customisation specific to Bunker Ramo.


In July 1971, Bunker Ramo filed US patent 3710060 “Push-button switch for mounting on printed circuit board”. The patent depicts a double-break switch that connects to the PCB by pressure alone, without the use of solder. Maxi-Switch manufactured a variant of this switch as Series 3100; their version used solder terminals. Deepak Kandepet discovered another variant of this switch in a Rockola jukebox panel. This variant—depicted below in photographs that he provided—also uses solder terminals. It differs further from Bunker Ramo’s patent than Maxi-Switch’s version, and it is unbranded, so the manufacturer is not known.

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Other side
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Opened, showing bifurcated, gold-plated double-break switch contacts

Bunker Ramo also filed US 3809838 “Modular push button switch assembly mounted on printed circuit board” in November 1971; the switch depicted in this patent is similar to that of the earlier patent mentioned above. This patent attempts to pass off the design as an encoding switch, with the claim “A further object of this invention is to provide a keyboard switch with a built-in encoding capability, eliminating the need of a separate encoding circuit.” However, the actual switch design has no encoding ability at all: upon actuation, current enters a single contact pressing and exits into one row and one column of the switch circuit. This is a kind of two-of-N arrangement, and would require similar circuitry to that of Micro Switch SW keyboards to convert from two-of-N to output codes. The semi-double-pole contacts permit two-of-N encoding without diodes, but offer no means to detect collisions without more advanced logic.