PURPOSE: To implement the additional service and other imposing processing to a subscriber accommodated in a mechanical exchange automatically without intervention of the operator of an attendant board.

CONSTITUTION: A relay exchange is provided with a charging pulse generating system consisting of an interpreter section 3, a charging pulse generating section 4, a charging rate arithmetic section 5, an additional service information reception section 6 and a detailed charging information recording section 7. The additional service information reception section 6 acquires charging control information relating to the additional service and call connection control information through inter-communication with a service control point 15. The interpreter section 3 calculates the charging the control information relating to a communication charge based on the acquired call connection control information. The charging rate arithmetic section 5 decides a period of a charging pulse based on the charging control information relating to the additional service and the charging control information relating to the communication charge, and the charging pulse generating section 4 generates the charging pulse based on the decided period and sends the pulse to the mechanical exchange.