PURPOSE: To allow a called subscriber to confirm a calling subscriber before answering by displaying the calling subscriber number on a called-side telephone set when the subscriber of an automatic section party telephone set PBX is connected to the subscriber of another PBX by dialing.

CONSTITUTION: The calling-side automatic private branch exchange PBXA and called-side automatic private branch exchange PBXB of a calling subscriber number display system are connected to a public station exchange CO through a trunk-line trunk COT and an extension subscriber circuit LC. A PB signal receiving circuit PBR and the trunk COT are connected mutually with the switch SW of the exchange PBXB, and the circuit PBR receives an incoming signal and an additional dial signal from a calling extension STAA. Then the trunk COT and a called subscriber extension STAB are connected together and number display control circuits IND and CONT connected to a CPU display the calling subscriber number on the called subscriber extension STAB, allowing the called subscriber to confirm the calling subscriber before answering.