2-20. CIPHER TEXT.
The RT can be used with a COMSEC device to receive and transmit cipher text (CT) information. The COMSEC
device is cabled to the RT at connector J5. Audio, data, and control signals are routed automatically.
When a cipher text signal is received, it is routed through the COMSEC device. See figure FO-11. The COMSEC
device will ground the IRNST(1)-P line to indicate CT operation. The received signal (RDCT) is routed to the
COMSEC device. The decrypted signal (AR/DDR) is returned to the RT. If it is an audio signal, it follows the normal
audio path. If it is a digital signal, it will follow the normal digital path. The COMSEC device provides the DDCO
When an audio signal is received in the FH and CT modes, the ECCM module deinterleaves the data stream. The
COMSEC device recovers the audio signal from the data stream.
When transmitting, the signal sent to the COMSEC device can be either audio (AT) or 16 kb/s digital (DDT). See
figure FO-12. The RED DDMC-N line is set to logic 1 for audio. It is set to logic 0 for digital. The COMSEC PTT-N
line is grounded for transmit. The audio control module routes the signals to the COMSEC device. The encrypted
signal (TDCT) is returned and routed to the switching module.
Audio and data signals are interleaved in the FH mode after encryption.
2-21. SNAP INTERFACE.
The RT provides seven signals for operation with a SNAP. The SNAP is cabled to J10 on the mounting adapter,
See figure FO-14. They are as follows:
The SNAP returns
Logic 1 = FH, logic 0 = SC.
Digital data stream that provides operating frequency.
Logic 0 pulse used with SERIAL DATA.
Clock used with SERIAL DATA.
Directs SNAP to perform self-test.
Logic 0 indicates RT is changing frequency.
Logic 1 = transmit, logic 0 = receive.
the results of its self-test on the FAULT6 line. If it fails self-test, the RT will display FAIL6.