TETRA Technology (Terrestrial Trunked Radio) was formerly known as ‘Trans-European Trunked Radio’. It is a European Telecommunications Standard Institute (ETSI) standard and the first version was published in 1995; It is a radio technology approved by the European Radio Communications Committee (ERC). It is specifically designed for use by government agencies, emergency services (police, fire, ambulance), railway transportation personnel for rail systems, transportation services and the military for public safety networks.

TETRA operates as time division multiple access (TDMA) with four user channels from a base station and 25 kHz spacing between carriers. System designs are made for both point-to-point and point-to-multipoint.

TETRA Terminals can communicate using direct mode operation (DMO) or trunk mode operation (TMO) using the switching and management infrastructure (SwMI) from TETRA base stations (TBS). DMO allows direct communication in situations where network coverage is not available. In emergency situations, this feature enables direct communication underground or in areas with poor coverage.

In addition to voice and dispatch services, the TETRA system supports various types of data communication. Status messages and short data services (SDS) are provided over the system’s main control channel, while packet-switched data or circuit-switched data communication uses dedicated channels.

TETRA creates a security gateway by authenticating terminals in the infrastructure and vice versa. Air interface encryption and end-to-end encryption are available to protect against eavesdropping.

Terminals can also make Full Duplex calls. TETRA terminals can communicate with other TETRA Users or PSTN via a full-duplex direct connection. Emergency buttons on the terminals allow users to override other simultaneous activities and provide emergency communication.

It provides up to 7.2 kbit/s per time slot in point-to-point connections and up to 3.5 kbit/s per time slot in the case of IP encapsulation. Both options allow the use of one to four time slots. Different applications include one of the previous connection features (both or neither) and one or more time slots. These rates are faster than competing technologies such as DMR, dPMR and P25.

There is a “compatible hardware” advantage that allows users to obtain terminals from different manufacturers. It is preferred by considering needs such as security, data communication, advanced features, number of channels and users.