The secure voice system provides the aircraft with speech security equipment for cipher and plain language operation of the UHF radio. The system consists of a signal processor, a Z-AHQ interface adapter and a Z-AHP remote control panel which are used in conjunction with the UHF and ICS systems. Coding of the six crypto-coded variables on the KY-58 is accomplished by using either the KOI-18 Tape Reader or the KYK-13 Automatic Transfer Device.

When cipher mode is selected, all transmitted and received UHF signals are encoded and decoded respectively. A green light marked “UHF CIPHER” on the advisory panel is illuminated indicating secure voice operation. In plain voice operation, audio signals are still routed through the secure voice system, but are no longer being encoded or decoded. The KY-58 has a feature called Plain Text Override, which enables the user to receive a plain text message while in the cipher mode.

Electrical power of 28 VDC is obtained from the DC essential bus and applied, via the RADIO MASTER No.1 switch and the No.1 radio bus, and through a circuit-breaker marked “SECURE VOICE” on the radio circuit-breaker panel, to the KY-58 remote control panel. From the control panel DC power is routed to the receiver-transmitter as operating voltage.