PURPOSE: To simplify the transport of an incoming call and at the same time to enhance the economical properties for a telephone exchanging system, by providing a telephone exchange common controller, a trunk control connecting part, a group controller and group control connecting part.

CONSTITUTION: When the P-th trunk TRKP has an incoming, the incoming is discriminated at the TRNP. Thus the telephone circuit number such as the number of TEL1 is sent to a telephone exchange common controller 4 via the TRKP and then a trunk control connecting part 5. Then the number of the TEL1 is sent to the controller 4 via a group control connecting part 7 and then a group controller 6. Thus the lamps corresponding to the circuits 1 of all key telephones KT within a group blink under the control of the controller 6. For instance, when the key corresponding to the circuit 1 is pushed with a telephone TELn (KT), the push-button information corresponding to the circuit 1 for the TELn is fed to the controller 4 via a route 6→7→4. The controller 4 connects the channel C between the TRKP and the TELn. Thus an answer is given to the incoming call from the telephone TELn.