The TSEC/KY-1 was an all tube, 50 KHz voice encryptor. The key generator was an nightmare to adjust. It was controlled
by a key card, just like the KY-3. Because it was 50KHz wide band device, it was restricted for local use to post, camp or stations and hardened sites.
Circa - 1959
1) George Mace <gmace8(at)comcast.net>
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