Importance

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Abstract

A time division digital communication system which does not require a common control unit for accomplishing interconnections, having a plurality of modular switching units. The switching units are identical and each unit has its own port circuits to which subscriber lines and/or trunks may be connected, service circuits, a time slot interchange and a microprocessor control and timing unit. The switching units are in direct communication via separate send highways, one for the port circuits and the other for the service circuits of each switching unit. The microprocessors of each switching unit are also in direct communication by way of control lines. The inter-switching unit send highways are connected to separate channels or groups of memory locations in the time slot interchanges of each of the switching units. By selective listening to receive highways connected to the output of the time slot interchanges, any port or service circuit, whether in its own switching unit or any of the other switching units, can be interconnected. These interconnections are made under microprocessor control on the basis of events such as off-hook conditions and dialed digits from the ports, rather than by central or call processing. The switching of calls is non-blocking, as any port can be connected to any one or more of the other ports or service circuits at all times.

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First Claim