TETRA (*TE*rrestrial *T*runked *RA*dio) is a professional mobile radio (PMR) system used
by public (police, military, emergency services) as well as private companies (public transportation,
harbour, industrial/chemical plants, power/electricity companies, etc.)

It is specified by the ETSI (European Telecommunications Standardization Institute).

The specifiations can be downloaded from

The main specification document is
  • ETSI EN 300 392-1 (Voice plus Data (V+D); Part 1: General network design)
  • ETSI EN 300 392-2 (Voice plus Data (V+D); Part 2: Air Interface (AI))
  • ETSI EN 300 395-2 (Speech codec for full-rate traffic channel; Part 2: TETRA codec)

For a good technical book on TETRA, check out Digital Mobile Communications and the TETRA System by John Dunlop and others.
You can preview it at Google books