Abstract: A communication terminal apparatus connected to a communication network through a data channel for transfer of line transaction data or packet transaction data and through a signal channel for control of a call to a communication destination party. Communication terminal apparatuses are connected to the communication network and subscriber numbers are usually previously designated, as identification data, to all subscribers of the communication network and as necessary, address data (referred to as subaddresses) arbitrarily set among some of these subscribers are attached to the subscriber numbers. These subscriber numbers and subaddresses are transmitted and received through the signal channel separately from transaction data transmitted and received through the data channel.

Abstract: Communication permission or rejection is controlled on the basis of a party terminal name data in a communication protocol to realize a security communication limited only between particular facsimile machines. Since a terminal name data as a unified communication parameter is used, a security system can be realized for such a large-scale system that different sorts of facsimile machines made by different manufacturers are mixedly connected.