IN-BAND RINGER

PROBLEM TO BE SOLVED: To provide an in-band ringer that can test entire lines from an exchange in a station leading to subscriber's terminals. SOLUTION: A current sensor 170 of the in-band ringer detect the current of a signal sent to a 4WS 11 and gives the detected current to a control section 180. The control section 180 discriminates whether or not a signal sent to the 4WS 11 is a signal for measuring conductors and allows a built-in switch drive circuit 181 to close a relay switch 162 in a switch section 161 to throw a relay switch 163 to the position of a terminal A and to throw relay switches 165, 166 in a switch section 164 to the position of a terminal A, when the signal sent to the 4WS 11 is the signal for measuring the conductors. Through the switching above, a line 20 and the 4WS 11 are physically connected and the signal for measuring the conductors is sent to a line loop configured with the lines.