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A station interface for a digital electronic telephone switching system is disclosed. The station interface couples a plurality of digital telephone instruments to a digital data bus having PCM encoded signals representative of analog voice signals time-division multiplexed thereon. The station inte

A station interface for a digital electronic telephone switching system is disclosed. The station interface couples a plurality of digital telephone instruments to a digital data bus having PCM encoded signals representative of analog voice signals time-division multiplexed thereon. The station interface enables two way communication between the telephone instruments and the digital data bus and includes a frame store memory for temporarily storing digital data on the data bus and assigning the digital data to system time slots. The output of the frame store memory is selectively supplied under microprocessor control to a digital audio processor which processes the PCM encoded voice signals from the telephone stations and supplies these signals to the audio processor. The audio processor digitally processes both the selected data from the frame store memory and the data from the telephone stations forwarded by a multiplexer, in respective system time slots, under microprocessor control. The PCM encoded signals are gain modified under the control of the microprocessor by the audio processor. The microprocessor monitors accumulated values of the energy of the voice signals originating at the telephone stations and those being forwarded to the telephone stations to dynamically alter the gain levels of the voice signals. In this way, differences in gain levels between signals originating from different sources, e.g. internal telephone stations or trunk lines, can be compensated. The station interface has particular application in controlling hands-free telephone station operation.

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Apparatus in a digital electronic telephone switching system for coupling a plurality of digital telephone instruments to a digital data bus having a plurality of time division multiplexed digital data channels allotted thereon, and for enabling two way communication between selected ones of said te

Apparatus in a digital electronic telephone switching system for coupling a plurality of digital telephone instruments to a digital data bus having a plurality of time division multiplexed digital data channels allotted thereon, and for enabling two way communication between selected ones of said telephone instruments and said digital data bus comprising: means coupled to said digital data bus for temporarily storing digital data transmitted on said bus, said storing means comprising a plurality of storage locations, each storage location corresponding to a channel of said digital data bus; first time division multiplexing means coupled to said telephone instruments for receiving a plurality of first signals from said telephone instruments and for converting said first signals into a first time-division multiplexed serial signal; second time-division multiplexing means coupled to said telephone instruments for receiving a second serial signal having digital data for each of said telephone instruments time-division multiplexed thereon and for converting said digital data of said second serial signal into a plurality of parallel serial data streams for each of said telephone instruments; control means including computer means coupled to said storing means for succesively selecting desired ones of said plurality of storage locations, thereby providing a serial selected digital data signal from the storing means; and processing means coupled to said storing means, said digital data bus and said first and second time division multiplexing means for digitally processing the serial selected digital data signal from said storing means and said first serial signal so as to modify the digital representation of the amplitude of voltage levels represented by said serial selected digital data signal and said first serial signal so as to produce a modified serial selected digital data signal and a modified first serial signal, said modified serial selected digital data signal being coupled to said second time-division multiplexing means as said second serial signal and said modified first serial signal being coupled to said digital data bus.