To reduce the number and quantity of communication times from a private branch exchange to a server.

Telephone terminal numbers are stored in a terminal management memory in private exchange 15 and a terminal management memory in server 1B. When idle/engaged state of a telephone terminal is shifted, a bit map editing part 16 recognizes the shift of the state through an extension interface 11, obtains the telephone terminal number of the pertinent telephone terminal from the terminal management memory 15 in private branch exchange and turns on or off a bit in a position corresponding to the telephone terminal number in a terminal idle/engaged bit map. A transmission data generation part 17 reads the terminal idle/engaged bit map at every second and transmits data for 1000 telephone terminals to a data transmission part 18. The data transmission part 18 transmits them to the server 24. A data reception part 19 receives data and transmits them to a bit map restoration part 1A. The bit map restoration part 1A restores the terminal idle/engaged bit map in the server 24.