PURPOSE: To attain surely the telephone charge management for individual or department, by providing a switch interrupting a DC loop of a line formed of an off-hook of a telephone set to a line connecting section of a managing device, and disabling the correspondence of the line with the said switch when a caller dials without inputting the own code.

CONSTITUTION: A magnetic card having a code number is prepared at each department using a telephone set 16 in common. When dialed without inserting a card, a card reader 9 can not detect a code number, but a line interruption switch S is in a state possible for correspondence, then a CPU1 detects an off- hook signal C2 of the telephone set 16. When the telephone set 16 hooks off, a DC loop of lines L1, L2 is formed, the CPU1 detects an off-hook signal C2 to make the line interruption switch S disable state in correspondence to interrupt the DC loop. Thus, the lines L1, L2 are not connected to the telephone set 16.