Application module interface for bidirectional signaling and bearer channels in a private branch exchange (pbx) environment

Abstract

An application module interface is disclosed that allows one or more modules to access voice or data channels in a private branch exchange environment that contains one or mole B channels (bearer channels) for transmitting voice or data signals, and one or more D channels (signaling channel) for transmitting data. The application module interface provides a control channel that allows a module to obtain and vary the status and configuration of a telephone terminal. The application module interface provides access to both directions of two B channels (Band B) and one D channel. The application module interface is the only interface required to connect the two B channels (Band B) and one D channel to or from the telephone terminal and the add-on module. A frame format includes a start bit (logic '1'), a number of data bits allocated to the D channels (D, D') and B channels (BBBB), and eight stop bits (logic '0'). A tip/ring, module allows an analog device, such as a facsimile machine or modem, to access the digital voice and data channels associated with the private branch exchange switch. An RS-232 or a Universal Serial Bus module allows a personal computer or other enabled device to interact with and control the operation of a telephone terminal for computer telephony integration applications.