Distributed switching and telephone conferencing system

In a digital telecommunication system, a method for conferencing a plurality of digital signals representative of voice communications, comprising the steps of:

• providing a memory having stored therein summation results of bits defined by signals applied to address inputs thereof;
• (a) selecting from a TDM bus a digital word defining a portion of an audio sound to be conferenced;
• (b) coupling the digital word to an address input of the memory for use in reading the memory;
• (c) temporarily storing memory readout data;
• (d) using the memory readout data together with a subsequent digital word selected from the TDM bus for accessing the memory to derive a summation signal;
• and
• (e) carrying out steps (a) through (d) for digital words received on the TDM bus in selected TDM bus time slots to define a final summation signal which is a composite of the digital words to be conferenced in a TDM frame interval.

A telecommunication conference circuit for combining voice information from plural sources, comprising:

• at least a pair of user port circuits adapted to communicate audio signals with respective audio sound apparatus;
• a TDM bus arrangement interconnecting each said user port, said TDM bus arrangement including duplicated TDM collection buses on which each user port transmits in respective dedicated time slots digital voice words, and duplicated TDM distribution buses on which each user port receives in respective dedicated time slots digital voice words;
• controller circuits for controlling the duplicated TDM distribution and collection buses, said controller circuits functioning to maintain one TDM distribution bus active and one in a stand-by status, and to maintain one TDM collection bus active and one in a stand-by status, said user ports, transmitting digital voice words on each TDM collection bus and receiving digital voice words from each TDM distribution bus;
• each user port including circuits for initiating a conference and setting up a conference by driving a duplicated TDM collection bus time slot with address information identifying another user port with which a conference connection is to be established, circuits for receiving acknowledgement information on other time slots of the duplicated TDM distribution buses from other user ports, a bus driver circuit for driving the duplicated TDM collection buses during a respective dedicated time slot with digital voice words representative of audio sounds, a bus receiver for receiving digital voice words of other conferenced ports from the duplicated TDM distribution buses, a circuit for specifying the time slots of the duplicated TDM distribution buses which are associated with user ports participating in a conference, a digital combiner for receiving digital voice words only from other user ports participating in the conference and for combining said digital voice words into a composite word for transferral to the audio sound apparatus.

A digital conferencing circuit for use in a time division multiplex (TDM) system, comprising:

• a combining memory having prestored therein summation results of signals presented to an input of the memory, said combining memory receiving addresses from the TDM system on an input of the memory;
• a result register having an input for receiving summation data output from the memory, an output of said result register being used as an input coupled back to said combining memory;
• and
• a time slot memory storing data associated with each time slot of the TDM system for indicating whether or not a voice word associated with each time slot is to be combined with another voice word, an output of said time slot memory being used to prevent said combining memory from responding to the voice words from the TDM system when said output of said time slot memory comprises a first indication, and to allow combining of the voice words when the time slot memory output comprises a second indication.

A method for conferencing digitized signals in a time division multiplex (TDM) system, comprising the steps of:

• writing a time slot memory with data indicating whether or not various time slots of the TDM system are to participate in a conference;
• presenting the digital signals of all TDM time slots to a combining circuit;
• reading the time slot memory in synchronization with TDM time slots to derive a memory output;
• and
• controlling the combining circuit with the time slot memory output to combine digital signals of respective time slots when the time slot memory output for the associated time slots comprise a first indication, and preventing the combining of digital signals when the time slot memory output comprises a second indication.

In a telecommunication system, a user port for carrying out communications with other similar ports via a TDM bus, comprising:

• a bus interface for communicating digital signals with the TDM bus;
• a user instrument interface for communicating audio signal with audio transducers;
• converting means in said user instrument interface for converting digital signals to analog signals, and vice versa;
• an identity uniquely associated with the user port;
• a conference memory;
• a processor programmed to:
• a) initialize high speed hardware circuits to retrieve digital signals from the TDM bus during time slots;
• b) select those digital signals associated with the time slots which are to participate in the conference;
• c) cause a series of memory addresses to be derived based on the selected digital signals for the conference time slot participants;
• d) cause the conference memory to be accessed with said derived memory addresses to produce a composite readout comprising an addition of each of the selected digital signals;
• and
• means for transferring the composite readout to said converting means in said user instrument interface so that said composite readout can be converted to an analog signal.

A telecommunication system, comprising:

• a time division multiplex (TDM) bus for carrying voice words between subscribers associated with the system;
• at least three user ports connected to the telecommunication system so as to be able to communicate voice words via the TDM bus, and each said port being dedicated for use with a single subscriber;
• a conference circuit in each said user port for combining voice words and for transferring corresponding analog signals to a user associated with the respective ports, one said conference circuit being dedicated for use with each said port;
• and
• a processor in each said user port for controlling the conference circuit to pass voice words therethrough substantially unchanged in a two-way telephone conference and to combine voice words in said conference circuit to produce different resultant voice words in a conference call involving three or more user ports.

A communication system, comprising:

• a plurality of user ports serving a plurality of user instruments;
• a time division multiplex (TDM) bus connected to each user port, a different time slot of said TDM bus being dedicated to each user port for communicating digital words, whereby a user port always communicates digital words on the same time slot;
• a bus timing circuit for providing timing signals to each user port to provide synchronization of each user port to a respective bus time slot;
• each user port including;
• a bus interface for communicating high speed digital words to and from the TDM bus;
• high speed hardware circuits for receiving and transmitting digital words with respect to said user port;
• a user instrument interface providing an interface between the user port and an associated subscriber instrument;
• and
• a processor programmed to initialize said hardware circuits for communicating high speed digital words between said bus interface and said user instrument interface, and to monitor status indications of the user instrument, said processor being programmed to respond to requests for service from an instrument connected to the port for communicating with another port by way of the TDM bus to establish a call path, to carry on bidirectional communications between users using the TDM bus, and to terminate the communication by signalling between the respective user ports using the TDM bus.

In a telecommunication system, a user port for carrying out communications with other similar ports via a TDM bus, said user port comprising:

• a bus interface for communicating digital signals with the TDM bus;
• a user instrument interface for communicating audio signals with audio transducers;
• a converter in said user instrument interface for converting the digital signals to the audio signals, and vice versa;
• a processor associated with each said user port and programmed to carry out call processing functions including establishing communications between said user port and said other similar user ports, a memory associated with each said user port and being accessible by a respective said processor, said memory storing busy/idle status indications of each said other similar user ports, said processor being responsive to requests for service from the user instrument interface to complete a call to a destination user port by accessing said memory to determine the status of said destination user port, and if said status indication is busy, said processor returns a busy indication to the user instrument interface, and if said status indication is idle, said processor compels communication via said TDM bus to said destination user port.

A communication system, comprising:

• a plurality of user ports serving a plurality of user instruments;
• duplicated TDM collection buses and duplicated TDM distribution buses defining time division multiplex (TDM) buses connected to each user port, said duplicated TDM collection buses for receiving digital words from each user port, and said duplicated TDM distribution buses for delivering digital words to each user port, and a time slot of said TDM buses being dedicated to each user port for communicating digital words;
• a bus timing circuit for providing timing signals to each user port to provide synchronization of each user port to a respective bus time slot;
• and
• each user port including,
• a bus interface for communicating high speed digital words to and from the TDM buses,
• high speed hardware circuits for receiving and transmitting digital words with respect to said user port,
• a user instrument interface providing an interface between the user port and an associated subscriber instrument, and
• a processor programmed to initialize said hardware circuits for communicating high speed digital words between said bus interface and said user instrument interface, and to monitor status indications of the user instrument, said processor being programmed to respond to request for service from an instrument connected to the port for communicating with another port by way of the TDM buses to establish a call path, to carry on bidirectional communications between users using the TDM buses, and to terminate the communication by signalling between the respective user ports using the TDM buses.