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TM 11-5821-333-12
ARRANGEMENT FOR DATA OPERATION WITH DRA.
a. Introduction. The following aircraft data equipment are compatible with the data rate adapter:
TACFIRE AN/PSG-2 Digital Memory Device
Airborne Target Handover System (ATHS)
Signals from these equipments are input to the radio through the aircraft intercom. Both types of data
equipment use frequency shift keying (FSK) signals. The DRA conditions the FSK to the 16 kb/s digital data
required by the RT. With data equipment in place, the radio set will still handle voice signals. The DRA recognizes
FSK signals. FSK signals are converted to data. Voice signals are not. Operation may be with both data and
COMSEC equipment. In that case, there are four types of operation:
Plain-text voice
Cipher-text voice
Plain-text data
Cipher-text data
b. Plain-Text Voice. The operator talks into the headset. Audio signals are routed from the intercom to the
DRA (through Z-AHQ, if used). FSK is not detected by the DRA. So the DRA routes the audio directly to the RT for
transmitting. Received audio from the RT is sent directly to the intercom, through the Z-AHQ, if used, and
otherwise through the DRA. The operator hears voice audio in the headset.
c. Cipher-Text Voice. The operator talks into the headset. Audio signals are routed from the intercom to
the DRA (through the Z-AHQ, if used). The DRA recognizes the signal as voice (not FSK data) and routes it to the
KY-58 where it is encrypted. The encrypted signal then goes through the DRA to the RT (through the Z-AHQ, if
used) for transmitting. A received signal is routed from the RT to the DRA (through the Z-AHQ, if used). The DRA
initially places the KY-58 in the data mode and checks for a preamble code word that identifies the signal as data.
This code word should be absent. The DRA then places the KY-58 in the voice mode and the signal is decrypted
and routed out to the intercom through the DRA (and Z-AHQ, if used). The operator hears voice audio in the
headset.
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1-20 DATA OPERATION WITH DATA RATE ADAPTER
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