What is TNM?

TNM likely refers to Terrestrial Trunked Radio Mobile, or TETRA. It is a professional mobile radio and two-way transceiver specification defined by the European Telecommunications Standards Institute (ETSI). TETRA is designed for use by government agencies, emergency services (police, fire, ambulance), rail transportation staff, transport services, and the military. It is mainly deployed in Europe, but is used in other parts of the world as well.