This standard is related to a radio system which uses 4FSK method (4-Level Frequency Shift Keying) among narrow band digital mobile telecommunication method as a mobile telecommunication system that uses 400MHz band and 150MHz band.

Among mobile telecommunication systems which use 4-level digital modulation specified in Article 57-3-2, Clause 1-1 of the Ordinance Regulating Radio Equipment, this standard specifies on a mobile telecommunication system that uses a novel modulation method (4-Level Frequency Shift Keying: 4FSK), and is a radio system principally based on voice telecommunication, and the like, and is relatively easy-to use and low cost in various wide business applications, such as promotion of a digital taxi radio system with the expansion of its utilization.

The 4FSK/SCPC narrow band digital mobile telecommunication system which is built as a self-supporting communication network comprises base station equipment and mobile station equipment, and it communicates between a base station and a mobile station or between mobile stations (via the base station or directly).

Also, the communication method is based on SCPC method in which one radio carrier corresponds to one radio channel, and one radio carrier enables a call service to one base station

A system described in Part 1 mainly controls the frame timing based on the reference of a base station, and is suitable for operation of such as controlling functionality.

Also, a system described in Part 2 mainly controls a frame timing based on the reference of a calling station.