To provide a communication terminal equipment enabling an optimum telephone terminal to be automatically determined when a plurality of telephone terminals are connected to a data terminal.

A plurality of telephone terminals 4 and 5 are connected to a data terminal 1 through connection cables 8 and 9 or by a wireless communication 10, or provided within the data terminal 1 by a card slot 11 or the like. The data terminal 1 includes a memory 2, a telephone terminal determining portion 3, reads data stored in first to third data storing portions 21-23 within the memory 2, and determines the optimum telephone terminals 4 and 5 by the telephone terminal determining portion 3, thereby enabling a data communication.