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Amphenol Corporation, formerly the American Phenolic Corp., is an American manufacturer. During the period of 1967–1982, Amphenol was owned by Bunker Ramo, resulting in their keyboard switch patents being filed by Bunker Ramo rather than Amphenol.

The following was noted in EE (Evaluation Engineering) in 1970:

If you can make connectors, you can make switches is the name of a new game. So it seems, anyhow. AMP and Amphenol have both jumped into the switch business. AMP is offering thumbwheels, rotaries and toggles. Amphenol brought out their 601 reed keyboard switches last fall. The firm’s keyboards are currently being introduced, and later in the year they will be bringing out lighted pushbutton switches according to a spokesman.


Presently, no Amphenol keyboards are known. The following text was included in their 1971 Electronic Engineers Master advertisement:

Most keyboard applications have very special requirements. Surprisingly few are alike. So we build a custom keyboard — one that’s made to meet your specs in every way. Just call your Amphenol Sales Engineer and tell him what you need, and we’ll take it from there.

Keyboard switches


In November 1970, Bunker Ramo filed US patent 3673526 “Magnetic switches and method and apparatus for making same” for reed switches that appear to be suitable for use in a computer keyboard. These switches were introduced by Amphenol as 601 Series. The switches were “designed to permit individual adjustment to specified operating point before leaving the factory.” The switches were also calibrated and tested in factory.

The specifications were as follows:

Contact resistance 200 mA maximum (initial)
Voltage rating 125 V DC, resistive load
Current rating 500 mA DC, resistive load
Power rating 10 W, resistive load
Form A (SPST-NO)

The following models were advertised in Electronic Engineers Master 1971–1972:

Part Description
601-R111A Spadetop for sloped keyboard
601-R211A Octagonal top for sloped keyboard
601-R311A Spadetop for stepped keyboard

Other configurations were available.

Amphenol 601 Series reed switches were also sold as Maxi-Switch Series 2700 reed switches.

The patent was transferred from Bunker Ramo to Amphenol in 1987.


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. These switches were advertised by Amphenol without a series name in Purchasing, Vol. 72 Issue 4, February 22, 1972 as follows:

Economy, long life claimed for keyboard switch

A keyboard switch rated at more than 10 million operations and called the industry’s most economical has been introduced by Amphenol. Designated 601-M11A, the switch has an operating force of 2.5 ± 0.50 oz. It features cruciform keytop engagement, and is said to be ideally suited to high-volume applications—for example, computer peripherals, typewriters, calculators, etc.

This advertisement gives the only known model number, 601-M11A. The implication is that these switches also fall under 601 Series, although that would have been a confusing decision to take. The “M” in “601-M11A” presumably denotes “mechanical”, complementing “R” for “reed” in the 601-R models.

Another advertisement, in Design News, volume 27, 1972, states:

Mechanical Keyboard Switch

Mounting directly to printed circuit boards, the 601-M11A switch has an operating force of 2.5 ± 0.5 ounces and a life rating in excess of 10 million operations. The bifurcated gold switch contacts are enclosed within a 0.625 inch square by 0.828 inch high housing, and are arranged to provide self-cleaning wiping action. The maximum contact bounce duration is given as 500 microseconds on touch typing applications and two milliseconds on hunt and peck applications. (…) Button pretravel is 0.100 inch minimum, stroke is 0.187 inch total. Bunker Ramo, Amphenol Controls Div., 419 South Arch St., Janesville, Wisc. 53545

As patented, these switches simply make pressure contact with the PCB instead of being soldered to it. 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 the patent than Maxi-Switch’s version, and is unbranded.

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

This patent was also transferred from Bunker Ramo to Amphenol in 1987.

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.


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