The KY-75 voice security system is used in conjunction with a HF command set to provide secure (ciphered, two-way voice communications). It was an analog voice device whose voice quality was poor and adjusting it was difficult.

KG-65 is manpack portable.
KG-75 is for shipborne and airborne operation.

This is not an image of the KY-75, only the remote control unit. (Courtesy TM 55-1510-220-10)

DESCRIPTION OF CONTROLS

Refer to above graphic.

1) RMT-LOCAL-SIG CLR switch - Selects operating mode.
a) RMT - In this position, the PLAIN/ CIPHER selection is controlled by input outside the KY-75 control panel.
b) LOCAL - In this position, transmit mode is controlled by PLAIN/ CIPHER switch.
c) SIG CLR - In this position, if a fill device is connected to the FILL connector, the alarms will be set, and the selected fill register will be cleared. Upon release of the switch (it is spring loaded to the LOCAL position) the TSEC/ KY-75 will request a fill variable from the fill device. If fill device is not connected, a steady tone signal will be transmitted to all other units within the net, indicating a desire to establish communications on that link.