PURPOSE: To display a call even when either line A or line B is positive by inserting a couple of light emitting diodes connected oppositely to a telephone set loop information display circuit and combining properly a contact of a CTG relay and the diode.

CONSTITUTION: A couple of photocoupler light emitting diodes poled oppositely are inserted to the telephone set loop information display circuit and a couple of CTGA, B relays CTGA, CTGB are connected in series with photo transistors (TR)A, B of the photocouplers in series, and contacts CTGA0 and CTGA1, CTGB0 and CTGB1 are connected in parallel with the diodes DA1, DB1 and the photo TRs A, B. Either of a couple of the photocouples is operated by a call, the CTG relay is activated, a current flows to either of the diodes DA1, DB1 and the call of a specific telephone set is displayed.