TETRA
Acronym for: TErrestrial Trunked Radio (formerly Trans European Trunked RAdio).
A specialist professional mobile radio (PMR) and two-way transceiver (walkie talkie), designed for use by emergency services, transport services and the military.
TETRA terminals can act as mobile phones, with a direct connection to the PSTN. The system uses Time Division Multiple Access (TDMA) with four user channels on one radio carrier and 25 kHz spacing between carriers. Digital data transmission is also included in the standard though at a low data rate. Both point-to-point and point-to-multipoint transfer can be used.
