The Tetra Standard

Like most standards, the Tetra standard is not a trivial document. There are many aspects which are covered in multiple documents. The idea of a standard is that people agree on a set way of doing things. Agreeing on all the ins and outs of something as complex as a digital radio communications system requires a LOT of planning and documentation. The organisation that looks after a lot of radio related standards is the ETSI (European Telecommunications Standards Institute). GSM? They wrote the standard. The test method to make sure DMR radios are safe? They wrote the standard. Link to ETSI website with a search on "Tetra"