Digital  Trunked Radio Systems  (DTRS) is the ground–ground radio communication for coordinating among users with the central system control which supports the frequency managing to a specific group of users operating in a wide area and many clients. This system comes with high security for data transmitting and is easy to use. The dedicated channels can be set up for communication with specific departments or individuals. Nowadays, AEROTHAI which is operating the Digital Trunked Radio System (DTRS) according to the TETRA (Terrestrial Trunked Radio) as recommended by the European Telecommunication Standard Institute, provides the rental service to the airlines at the main domestic airport throughout the country as well as oil and gas business at Map Ta Phut Industrial Estate, Rayong. This service offers both standard and intrinsically safe Handie Talkie which is operated in the airside and dangerous areas, also mobile radio communication for desktop/vehicle.