Tetra (Terrestrial Trunked Radio) is another new open digital radio standard which is defined by the European Telecommunications Standardisation Institute (ETSI) to meet the needs of professional mobile radio users. Tetra is being widely deployed in the UK for use by the Emergency Services and the RAF.

Tetra differs from conventional mobile phone services as it is configured to act both as a 'walkie talkie' and as a telephone. The push to talk button gives instant access to a group of users, just like a conventional police radio. Alternatively, the handset can be used to reach a specific number, including a normal phone.

Tetra also carries a data service, allowing police cars to access computer databases and maps.

Tetra operates at a much lower frequency than mobile phone services (400MHz), and needs a smaller number of sites. Some concern has been expressed about the safety of Tetra handsets, but police forces, airports and fire fighters around the work are adopting it. The concerns about handsets do not extend to base stations.

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