Pro-M Professzionális Mobilrádió Zrt. (Pro-M. Zrt.) is member of the NISZ Group. Pro-M Zrt. was responsible for the implementation of the Unified Digital Radio Communications System (EDR) in Hungary. At present the company is in charge of the operation and development of the EDR system. The purpose of the closed radio communications system of very high availability is to implement professional connection between the different emergency and law enforcement bodies in order to enable them to implement their tasks faster, more efficiently and securely. The EDR works with the TETRA technology, which acronym stands for Terrestrial Trunked Radio system. TETRA is a mobile communications system designed for professional use, with the help of which the group communication services, the customized combination of mobile telephony, messaging and mobile data service can be reached from a single radio unit. The current users of the EDR service operated by Pro-M Zrt. include the National Police Command, the Hungarian Customs and Finance Guard, the organizations of the Firefighting Service, the National General Directorate for Disaster Management, the National Directorate General for Environment and Nature Protection and Water Management, the National Ambulance Service, the Air Ambulance Service, the National Command of the Hungarian Prison Service, the Hungarian Army and the National Security Services.