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Raytheon KBSR and KBFR



KBSR and KBFR are collectively a series of reed keyboard switches from Raytheon. These are not necessarily series names; KBSR is the model number prefix for the reed switches with a 10° sloped base, and KBFR is the model number prefix for switches with a flat base. Although people have claimed that these switches are made from glass tubes—such as from Raytheon’s vacuum tube (thermionic valve) tooling—Raytheon advertised the switch shells to be made of polycarbonate.

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


The models listed below are taken from an advertisement in Electronics magazine from November 1969. The diagram for KBFR-9/KBSR-9 is clear, but the design is unconventional: it is equivalent to a DPST-NO switch with the two inputs connected. That is, a single common terminal supplies two output terminal, with each output having a separate reed capsule inside. The reason for such a design is not known.

Model Type Angle NSN
KBFR-1 SPST-NO momentary
KBSR-1 10° 5930-01-017-0751
KBFR-2 Double action
KBSR-2 10°
KBFR-4 SPDT momentary
KBSR-4 10°
KBFR-6 SPST-NO illuminated
KBSR-6 10°
KBFR-7 SPST-NC momentary
KBSR-7 10°
KBFR-9 Dual contacts, dual outputs
KBSR-9 10°

The illuminated models KBSR-6 and KBFR-6 have an unusual design. A lamp socket is placed on either side of the switch; the illustration for KBSR-6 in the advertisement carries the description: “Backlight function KBSR6 switch with two lamps for added protection.”

Note that the hyphen in the model numbers is sometimes omitted.


The following specifications are taken from an advertisment in Radio Electronica magazine in the Netherlands, placed in the 1st of May and 1st of June issues in 1969. The operating force could be customised, and differed between advertisements, being listed as 3 ounce in 1967 and 2.5 ounce in 1969.

Characteristic Single action Double action
Pretravel 332″ (2.38 mm) 116″ (first level)
332″ (second level)
Total travel 532″ (3.97 mm)
Operating force 2½±1 oz (71±28 g) 2½±1 oz (first level)
17±5 oz (second level)
AC contact rating 12 VA maximum
DC contact rating 250 mA at 32 V
Rated lifetime 10 million cycles
Operating temperature −55 to +65 °C
Contact material Noble metals (rhodium-plated)
Bounce time 1 ms

Switch model “KBSR1” has is given in the NSN record as being 1.156″ tall and 0.625″ in diameter.


One keyboard is known Raytheon reed switches: Raytheon assembly 226274 (there were 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 what appears to be KBSR-6 without a lamp fitted; the leads for the lamp socket can be seen. 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.


All documentation below was scanned by Bitsavers unless otherwise noted.