The invention relates to a switching arrangement for telecommunication switching systems, particularly telephone switching systems, and more particularly switching systems having a switching network made up of switching matrices in several switching matrix stages interconnected via links, wherein all trunks (e.g., subscriber lines, local interexchange trunks and long-distance trunks) and all inlets and outlets of switching equipments (e.g., selecting receivers, connector sets, and the like) necessary for the call setup and call supervision for each connection are connected to the inlets of the first switching matrix stage of the switching network, and wherein outlets of the switching matrices of the first until the next to last switching matrix stage are connected to the inlets of the switching matrices of the succeeding switching matrix stage and are capable of being interconnected in pairs therein.
A switching arrangement of the type referenced hereinabove has become known through U.S. Pat. No. 3,527,895 (FIG. 2). The trunking scheme of the switching network shown therein is known as the "reversed trunking scheme". In accordance with the reversed trunking scheme described in the latter patent the inlets of the switching network have connected thereto subscriber lines, local interexchange trunks, and all switching equipments necessary for the call setup and call supervision, evenly distributed throughout all the inlet switching matrices of the switching network.
Another technique known through U.S. Pat. No. 3,665,110 is to subdivide a switching network having a reversed trunking scheme into various switching network sections and to connect the outlets thereof individually in pairs from switching network section to switching network section. In this case, subscriber stations, local interexchange trunks, long-distance trunks, selecting receivers and all the switching equipments necessary for the call setup and call supervision are connected to each switching network section.
The problem to which the present invention is directed is to provide a means for the expansion in the simplest way possible of switching systems of the type defined hereinabove. In the switching system disclosed in U.S. Pat. No. 3,665,110, the addition of a further switching network section is difficult, because the outlets of the existing switching network sections are interconnected individually in pairs from switching network section to switching network section according to a very specific connection arrangement. In this prior art technique, when a switching network section is added, the pairwise interconnection of outlets of existing switching network sections should be eliminated at least in part and the arrangement of the interconnection changed.
In addition, when expanding telephone switching systems, it is impossible to predict if the switching equipments are to be enlarged with respect to increased internal, external, or transit traffic. Thus, when enlarging a switching system it can be a question of solely making connectable subscriber stations, internal connector sets and selecting receivers, but it can also be a question of solely making connectable connection sets, registers, and forwarding sets. Moreover, a switching system may have to be expanded in both respects.
It is an object of the present invention to provide means for expansion of a switching system of the type referred to hereinabove in the most adaptable way possible and to carry out any necessary provisions therefor on a limited scale only.