| 摘要 |
A modular switching system for terminating and originating calls between central office subscriber lines and local stations provides the appearance of a business environment to an establishment served by one or more central office lines and as few as one local station. Central office lines may comprise standard subscriber lines or PBX trunks. The switching system includes one or more master switching units (102, 112) equal in number to the central office lines which are seved by the system; and a plurality of station switching subsystems (120, 130) corresponding in number to the local stations served by the switching system. Each master switching unit includes a main port for connection to a telephone answering device (TAD). A TAD comprises a manual attendant's module and/or an automatic telephone answering set to provide a recorded audio announcement (OGM) which advises a calling party how to proceed to complete a call to a particular local station served by the called central office number. In response to subsequent DTMF call signalling information received from the associated central office subscriber line, the mast switching module disconnects the TAD from the central office line; and connects the calling central office line to a local station defined by the received call signalling information.
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