Path search circuit

Claim 2

A time division multiplex data switching central exchange operating in pulse code modulation in which the operations are controlled by a data processing machine; the said switching central exchange comprising a switching network; circuits for a group of p-trunks, where p is the number of digits of each channel message, connected to the inlet of the switching network and provided for carrying out on reception a series-parallel conversion and, on transmission, a parallel-series conversion of the digits of the messages of channels of p-trunks; circuits of detection and interpretation of the signalling digits associated with each circuit of a group of p-trunks comprising mainly a signalling memory in which are stored for each channel of the group the state of the expected signalling and the indication of the change, if any, of the signalling state with respect to the expected state; junctor data memories connected to the outlet of the switching network; each junctor comprising, in addition to a data memory, a time path memory and space path memories for setting up a connection between two channels; the said memories being up-dated by the data processing machine in relation with communications in course; a clock circuit provided for supplying cyclic signals; said scanning and path search device controlled by the data processing machine for processing the signals supplied by circuits associated with the circuits of group of trunks, with the signalling memories and with the space path memories; said scanning and path search device detecting the alarm signals from the trunks, the new calls and the other changes of state of the signalling as well as the search for a free path and the identification of busy connections.

Claim 3

A data switching central exchange according to claim 1 in which the scanning and path search device is characterized by the fact that in each circuit of a group the alarm signals of the trunks appear at each digit time slot during which is processed a channel belonging to the said trunk; by the fact that the signalling memories are read in a cyclic way and the signals read are applied to logical circuits which detect for each channel of a group the new calls and the other changes of state of the signalling; by the fact that the space path memories are read in a cyclic way and the space codes read are applied to a comparator which receives on the other hand the space code supplied by the data processing machine, the said space code identifying a cross-point of the switching network in the case of an identification of a busy connection or which does not correspond to any cross point at all in the case of a search of a free path; by the fact that circuits are provided for storing and decoding the information necessary for the operation of the scanning and search path device, the said information being supplied by the data processing machine; by the fact that the signals supplied by circuits of group are connected to a same switch; by the fact that logical circuits associated with the signalling memories corresponding to the circuits of a group connected to a same switch; and by the fact that comparators associated with the space path memories of the junctors connected to a same switch are applied to a sequential logical circuit which determines the time and space coordinates of the trunk in alarm or of the calling channel, or of the channel which changes its state without being calling or of the free path or of the busy connection to be identified.

Claim 4

A data switching central exchange according to claim 1 in which the codes of masks are supplied by the data processing machine; the said codes of masks enabling, in the sequential logical circuit, to take into account only the alarm signals coming from certain circuits of groups of trunks of a supergroup or the signals of changes of state coming from logical circuits associated to certain signalling memories of a supergroup, or the identity signals coming from comparators associated to certain space path memories of a superjunctor or the signals concerning certain channels.

Claim 5

A data switching central exchange according to claim 1, in which the sequential logical circuit is characterized by the fact that the duration of a scanning concerning the alarms, or the new calls or the changes of state other than the new calls as well as the duration of a search for a free path or the identification of a busy link is limited.

Claim 6

A data switching central exchange according to claim 1, in which the switching network comprises two stages characterized by the fact that the search of a free path between two calling channels at the time slot t''x and one of the allowed outgoing channels at the time slots t''y defined by a code of mask is carried out in two parts; the first part consisting in searching a free link between the two stages of the switching network at a time slot t''x, the second part consisting in searching a free junctor at a time slot t''x and at one of the time slots t''y as well as a free link and a free outgoing channel at a time slot t''y during which the junctor, which is free at the time slot t''x, is also free.

Claim 7

A data switching central exchange according to claim 1, in which the switching network comprises two stages characterized by the fact that the identification of the path used for a connection with an incoming channel at the time slot t''x is carried out into two parts, the first part consisting in identifying link used at the time slot t''x and the second part consisting in identifying the junctor used as well as the time slot t''y of the outgoing channel.