Abstract: A station controller for use in a telephone system includes a plurality of digital telephone stations comprising one or more multi-station pick up groups, each having a primary station and one or more associated secondary stations for picking up calls to the primary station. The secondary stations generate a pick up signal to initiate pick up of a call to the primary station and have indicating lights or the like. A centrex exchange is connected to a station controller through a digital carrier link and the station controller is connected to the telephone stations by digital links. The station controller includes a monitor for monitoring the status of each primary station and generating a status signal, and controls the status of the indicators of the secondary stations responsive to the status signals.

Abstract: A modem receiver having receiver control, signal detection, and data demodulation implemented with a single general-purpose integrated circuit microcomputer. Novel multirate digital signal processing techniques are included which provide complete real-time recovery of all data and modem signals in a microcomputer integrated circuit having an architecture not optimized for signal processing applications. The resulting techniques extend to more general signal processing applications which may be implemented by other general-purpose microcomputers, programmed signal processors, or specific dedicated hardware logic. The novel modem receiver includes digital FIR filters, performing quadrature signal detection, and post-demodulation data correction with an all-digital second-order carrier recovery loop.

Abstract: A data modem is provided which is operative at a data rate of 4800 bps and employing 8 phase DPSK modulation. The modem includes a microprocessor and associated memories for digital signal processing and control of substantially all transmitter and receiver operations.