Section II. EQUIPMENT DESCRIPTION AND DATA
1-8. PURPOSE AND USE
Provides single channel, one-way reversible, or duplex communication in line with radio transmitters and
Converts dc mark and spaced pulses into audio tones.
Converts audio tones into dc mark and space pulses.
Used with any standard teletypewriter equipment using 20-or 60-milliampere inputs and outputs.
Converts dc marks and spaces to audio tones that modulate radio transmitters for signal transmission to
Converts signal received from distant transmitters into marks and spaces for printing on a teletypewriter.
Signals received and transmitted are frequency-shift-keyed (fsk), radio frequency (rf) signals.
1-9. LOCATION AND DESCRIPTION OF MAJOR COMPONENTS
See TM 11-5805-387-10-2.
1-10. DIFFERENCE IN MODELS
There are several physical and electronic differences between this modem and Modem Radio Teletypewriter MD-
522/GRC. For a complete description of MD-522/GRC, see TM 11-5805-387-10-1.
1-11. EQUIPMENT CONFIGURATIONS
The modem is always used as a component of a radio teletypewriter system. The modem's function in a radio
teletypewriter system in shelters AN/GRC-142 and AN/GRC-122 is described in TM 11-5815-334-12.
1-12. SAFETY, CARE, AND HANDLING
Safety instructions are on the warning page found inside the manual 6 front cover.
Be very careful when cabling the modem. Connectors and cable assemblies are keyed for easy installation. The
equipment may be damaged if cable assemblies are not properly aligned.
Carry the modem by both handles at all times, even though it is lightweight.
Read all warnings, cautions, and notes. Think safety!