PURPOSE: To allow a caller terminal equipment to read a caller terminal number from transmission data and to register the number to its own terminal equipment in one-operation and required by extracting the caller terminal equipment number from an arrived signal and registering the caller side terminal equipment number to be extracted into a memory.

CONSTITUTION: A caller terminal equipment 1 connects to a called terminal equipment 4 via an exchange system 3 and a communication line 2. A data processing section 8 and a tentative storage reception circuit 5 storing tentatively a caller terminal equipment number are connected to a called party terminal equipment 4. The tentative storage reception circuit 5 is connected to a one- operation memory circuit 6 through a registration switch 7, and the registration switch 7 is used to write a caller number of the caller terminal equipment 1 by the user of the called side terminal 4 when the caller number is desired to be registered in the one-operation memory circuit 6 during communication. Thus, the terminal number of the caller is registered to its own terminal equipment by a simple operation of depressing a button of the registration switch 7 with respect to an incoming call.