The RRS-7 is a single-channel radio relay system for the transmission of
a single telephone channel (300-3400 Hz). It is used to extend two- and
four-wire telephone lines wirelessly. It can be connected to automatic and
conductor-type telephone sets.
See Jane's 1988, p. 245.
Frequency range: 235-270 MHz
2 x 1000 duplex channels with 25 kHz channel spacing
Power output: 500 mW
Mode: F2E with ±10.5 kHz maximum deviation
Power supply: 12V DC, NiCd battery 7Ah
Power consumption: 3W (standby), 7W (duplex operation)