PURPOSE: To construct a system strong against interference disturbance by shifting automatically a time slot to the time slot of longer guard time when radio interference arises and communication quality is deteriorated, and if the time slot can not be shifted, narrowing the width of the time slot by lowering highest frequency by a low pass filter.

CONSTITUTION: An interference disturbance detector is installed previously in mobile radio equipment or a radio base station, and when it is detected that the disturbance arises, the time slot during communication is changed successively to the slot of the longer guard time. If it is impossible because of the congestion of traffic, the low pass filter is inserted in respect of a signal to be inputted to a signal velocity conversion circuit 51a. Simultaneously with this, an instruction to increase time compression ratio (1/n) 2.4/3.0-times higher than 1/n in the past is given to the signal velocity conversion circuit 51a-1. The guard time between the time slot SDa-1 and the time slot immediately before it is greatly increased, and the radio disturbance to the time slot SDa-1 due to multi-frequency propagation is greatly reduced.