PURPOSE: To discriminate the propriety of a charging pulse from a centralized station by allowing a slave station to collate whether a charging pulse incoming from the centralized station is in matching with its charging index or not.

CONSTITUTION: A received number is expanded in a reception number expanding section G, charging indexes M1∼M14 are extracted by a translation circuit H and a period pulse corresponding to the extracted charging index is received by a periodic pulse drawing section F and locked to an MP collating circuit N. When an outgoing sender 2 finishes transmitting the MF signal, since an S relay of a toll outgoing trunk 9 is restored, a charging collating device 10 restores an ST relay, and the locking of the line is released by the restoration of an st contact. A charging pulse is incoming from the post-position by the talking of a sender subscriber - called party, the subscriber call meter is registered by the operation of the M relay and the MP relay is activated through an m-contact with the same pulse. Thus, whether or not the charging pulse from the centralized station is correct is discriminated by a slave station.