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Raytheon

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Overview

During their long history, Raytheon are so far only known to have made one model of keyboard. Likely other models exist, that have yet to be discovered, which would fit with there seeming to be three different models of Raytheon keyboard switch known.

Switches

Raytheon introduced reed and mechanical switches in the late 1960s, around 1967; these advertisements can be found under Documentation below. The reed and mechanical types both take the same form, that of a transparent cylinder, with a flat metal keystem.

KBSR-1 and KBSR-2

KBSR-1 and KBSR-2 are Raytheon’s known reed types. KBSR-1 is a standard momentary switch, while KBSR-2 is “double-level” switch that may indicate double action. KBSR-1 has 3 oz operating force and a 10 million cycle lifetime. Model KBSR-1 can be seen in a 1967 advertisement, where the model number can be seens printed on the switches. Contrary to claims, Raytheon advertised the switch shells to be made of polycarbonate, rather than glass.

One keyboard is known with switches matching those in the advertisement, Raytheon assembly 226274 (additional photos on eBay of the same unit). The eBay seller reported the switches to be model “KB-SR1”, with no supporting evidence, and the switches are reported on Deskthority to be made of glass. The Call key has a 1.75-unit keycap and along with it a different switch shell that may be designed to support a stabiliser, but no such part is present. This keyboard is claimed to be from the 1960s, and the one visible IC date shown on Deskthority is from early 1969; this fits with the apparent time at which the switches were introduced. The switch encoding is provided by a diode matrix, as is typical for that era.

Switch model “KBSR1” has NSN 5930-01-017-0751, and is given in the NSN record as being 1.156″ tall and 0.625″ in diameter.

No patent has been discovered for these switches, and the double-level type has yet to be observed.

KBSM-1

KBSM-1 is a mechanical switch type introduced around the same time. The switch uses a bridge contact arrangement, with wiping contacts. Bounce time is said to be less than 10 milliseconds, and the rated lifetime appears to be the same 10 million cycles as the reed type. A single confirmed example of this switch exists, depicted in eBay listing “1 vintage new in box NOS Raytheon KBSM - 1 …”, already sold in August 2020.

The 1967 advertisement indicates that double-level wiping-action switches were also available, so there should be a KBSM-2. This model was not listed in the 1968 advertisement where the model numbers are given.

Meryl Miller collected a sample of a very similar switch, which he reported as having a glass shell:

(At the top left is MEI T-15 sealed; below this is what appears to be Cherry M62-0100 from before 1980, an unknown type, and finally what appears to be Raytheon.)

The design is almost the same, but the contact shape differs at the protrusion point, and the contact material is not the same bright gold colour. The following diagram was drawn based on analysis of Meryl’s example, and it matches up in principle with the example later discovered on eBay:

Specifically, the plunger itself acts as a bridge that connects the movable contacts to each other. A tapered section keeps it clear of folded projections in the movable contacts. As the plunger is depressed, the width of the plunger at the height level with the projections becomes sufficient to make contact with them, and current can flow from one movable contact to the other via the plunger. To allow for ovetravel, the movable contacts flex to accommodate the plunger, providing a wiping action that keeps the contact surfaces clean.

Both Meryl’s example and the example on eBay have sloped bases, which is a less common way of achieving a stepped arrangement. Instead of an angled plunger, the base of the switch itself is stepped. This can also be seen in Navcor, George Risk KB and Fujitsu FES-5 reed switches.

No patent is known for this design either. In August 1971, Raytheon filed a patent for a bridge contact switch. In 1973 they were granted US patent 3725625 “Mechanical pushbutton switch with pointed end coil spring contact”. One of the illustrations from the patent is reproduced below:

The shell is described as being from a material such as “glass, plastic or ceramic”. A shorting bar is brought down over a pair of coil springs; these have sharpened ends so that they do not slide across the shorting bar, itself suggested to be roughened for the same reason. The use of coil springs provides overtravel: they can be compressed once the shorting bar makes contact with them. This suggests that these switches may have a progressive rate with knee force curve.

Tactile keycaps

In January 1973, Raytheon filed a patent (granted in 1974 as US patent 3822776 “Tactile keycap”) for a tactile mechanism placed inside the keycap itself. This mechanism appears to be designed to provide overtravel as well as operator feedback. Both click feedback and silent options were proposed.

Documentation