PURPOSE: To make the equipment small by implementing individually protocol conversion and line connection processing to each of different communication systems and allowing a data terminal equipment to adopt same signal format and protocol processing.

CONSTITUTION: In the case of communication from this mobile body communication equipment 1, a call request signal from the terminal equipment 1 is inputted to a satellite line connector 13 via a changeover device 12, in which format conversion of a call request signal and protocol conversion for line connection by taking satellite propagation delay into account are implemented and a modulation wave after modulation is outputted via a MODEM 15 and an antenna 16 and the wave is sent to an opposite station via a communication satellite 2. After the opposite station confirms enable communication, the station sends a communication enable signal to a mobile body 1. The mobile body 1 processes the signal in the reverse order to above and confirms the output enable signal from a terminal equipment 11 and starts communication. In the case of communication from the opposite station, the mobile body communication equipment 1 receives a signal at an antenna 16 and processes the signal in the reverse order to make communication. When a ground radio line circuit is in use, the connection between the terminal equipment 11 and the line connector 14 is selected by the changeover device 12 and the signal is similarly sent/received. How to use protocol conversion or line connection is not required and miniaturization is attained.