In around '79 or '80 we were equipped with Vinson secure units for our tactical radios, which I believe were frequency-hopping. Before that our secure units consisted of devices with male rods that fitted into female recepticles, and the settings on the device had to be changed daily according to that day's settings specified in the Communications-Electronics Operating Instructions. However, call signs then included in the CEOI did not have unique suffixes that identified the specific element within the organization.
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