This invention relates to information transmission systems of the type in which the transmission capacity between nodes of a trunk network is shared between circuit-switched and packet-switched traffic.
British patent specification No. 892399 (STC) is one of the pioneer disclosures of methods of combining two different sorts of traffic over the same communications path. It discloses a TDM-PCM system in which the TDM channels are usable for high priority (e.g. speech) intelligence or low priority (e.g. data) intelligence. When a silent period in the high priority intelligence occurs, low priority intelligence is sent. This increases the amount of traffic which can be handled by the communications path.
A more recent extension of the general principle of increasing the amount of traffic to be handled is described in British patent specification No. 1486105 (IBM). This is a TDM system in which circuit-switched traffic has first option on the system's time slots, but store and forward traffic is sent in gaps in the circuit-switched traffic. This further improves traffic handling capacity of such a system.
Other Patent Specifications of interest in the present context are British patent specifications Nos. 1005075, 1021927, 1043447, and 1186385, and European application Ser. No. 0082333Al.