PURPOSE: To simplify the circuit constitution by comparing phases between in use-spare circuits by a code synchronizing signal of an error correction code, allowing data signals of the in-use and the spare radio circuits to coincide with each other and switching them.

CONSTITUTION: In a synchronization switching circuit 15, a code synchronizing signal W12 of a spare radio circuit and a code synchronizing signal W13 of an in-use radio circuit are compared, and by allowing the phases to coincide with each other, a data signal D17 of the spare radio circuit and a data signal D18 of the in-use radio circuit are both interlocked and are in phase. In such a way, the device is constituted so that the synchronization can be switched, and synchronization switching data is outputted as a data signal D19. In such a way, both of a redundant bit and an overhead bit are deleted by a single reverse speed converting circuit 14, and the constitution of a speed converting circuit and a reverse speed converting circuit is simplified.