Abstract: An interface circuit for a telephone instrument forming part of a character display phone PBX system. The circuit is connected to receive data signals indicative of the condition of the character display and keyboard portions of the instrument, and to store and manage the incoming data and produce a serial RS232 output for communication of the data to a computer or terminal device. The interface enables the use of a computing device to store large amounts of information related to potential calling parties and called parties which may be identified in the display of the telephone instrument and also to associate such information with messages entered into the computer via the keyboard. The overall system thus enables custom answering of a multiplicity of lines of such a character display phone system and use of a single multi-line phone as a messaging center.