Ralph Simpson introduces the KY171/172.

"The KY-171 Audio Frequency Coder was used in the Mercury Project (the first US space flight program that put Alan Shepard in space and John Glenn in orbit).  This was paired with the T-560B transmitter to communicate with other ground stations and the space capsule.  The receiver was the R-669A which used the KY-172 Audio Frequency Decoder.  All these devices were part of the radio set AN/FRW-2 (406-549 MHz),  which as far as I can find was first introduced in 1956 and originally used for sending ballistic missile telemetry".

Credits and Contributors:
1) Ralph Simpson <ralphenator(at)>
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Aug 18/11