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Raytheon

Contents

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

The Raytheon switches discovered thus far have shells that take the form of glass tubes. It seems that, as a vacuum tube (thermionic valve) manufacturer, Raytheon used their existing ability to manufacture glass tubes to produce keyboard switches.

Reed

Little is known of Raytheon’s reed switches. No patent has been discovered for them. They are known from a single keyboard, Raytheon assembly 226274 (additional photos on eBay of the same unit). The eBay seller reports the switches to be model “KB-SR1”, with no supporting evidence. “SR” could denote “switch, reed”. This model (as KBSR1) has NSN 5930-01-017-0751, and is given in the NSN record as being 1.156″ tall and 0.625″ in diameter. The shell is transparent, and is 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.

The keyboard itself is claimed to be from the 1960s; the one visible IC date shown on Deskthority is from early 1969. The switch encoding is provided by a diode matrix, as is typical for that era.

Mechanical

In August 1971, Raytheon filed a patent for a bridge contact switch. In 1973 they were granted US patent 3725625. 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.

These switches have yet to be seen. The only discovered Raytheon mechanical type is one that Meryl Miller collected as a sample. He reports that this type also has 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 following diagram indicates how it appears to work. The diagram is based on the photograph but some of the details are guesswork only. It appears that the more complex arrangement of a shorting bar and coil springs (as shown in the patent) was replaced by simple metal leaf contacts whose flex provides the overtravel. The contact shapes are reminiscent of the tactile version of Hi-Tek Series 725 but in this case the design appears to be linear.

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.

In reality the operation may differ, as it is not possible to see all the details through the shell in the photograph. However, this description matches up with what Meryl remembers of the switch. It would seem reasonable that the sides of the plunger and the projections on the movable contacts bear some kind of precious metal plating or inlay to improve contact reliability, but this cannot be determined from the photograph either.

Meryl’s example also appears to have a sloped base, 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 George Risk KB and Fujitsu FES-5.

Tactile keycaps

In January 1973, Raytheon filed a patent (granted in 1974 as US patent 3822776) 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.