Patent GB-637731-A (GB)
Title: Improvements in telephone systems
IPC: H04M15/38
Filed: 1947-02-21
Abstract: 637,731. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Feb. 21, 1947, No. 5137. Convention date, Feb. 23, 1946. [Class 40 (iv)] A system providing. automatic ticketing of connections comprises means for connecting calling line and called line number registering means separately to the recorder, linking circuits for extending the call being connected to the recorder at the same time. In this abridgment a number in parenthesis indicates the figure in which the apparatus is shown, reference being had to Fig. 1 which indicates in square brackets those figures which have been omitted. Conductors have a hundreds digit equal to the number of the figure in which they originate. A " district j unctor " means a circuit in the originating exchange linking the secondary line switch with the primary switch of a district frame, and operates as a feed circuit to supply talking battery to the calling subscribers and to supervise the originating end of connections. A district frame is an assembly of primary cross-bar switches and secondary cross-bar switches linking the district junctors with outgoing trunks. The district junctors are matched at the terminating exchange by line junctors which supply talking battery to the called subscribers. The subscribers' lines (21) are arranged in groups of ten connected to the vertical terminals of a primary 10 X 10 crossbar switch, the horizontal terminals being connected to line links such as 2115-7, one to seven switch units, constituting a horizontal group, being connected in multiple to the group of ten line links. Ten horizontal groups constitute a line frame, which may be regarded alternatively as one to seven verticals. The line links are distributed to a frame of 10 secondary 10 x 20 cross-bar switches (22), each divided into halves for connecting with district and line junctors respectively for extending originating calls or terminating calls as the case may be. For each line frame a line link control circuit controls the selection of line switches in extending a calling line to an idle district junctor, and for each district frame, a sender link control circuit (35-47) assists the line link control circuit in selecting a district junctor and controls operation of the sender link switches to connect an idle sender with the selected district junctor. A recorder (8-13) serves each district junctor frame (64, 66, 68, 70). General operation of establishing a connection. A calling subscriber is located by the line link control circuit by determining the primary cross-bar switch in which the line is located and the particular vertical unit on which the line is terminated. The line link control circuit simultaneously selects an idle line link between the primary switch in which the line appears, and a secondary switch connected to a group of district junctors with at least one idle district junctor having access to idle senders and to an idle sender link. The sender link control circuit then selects an idle district junctor from the group and selects an idle sender and an idle sender link. A connection is thus established from the calling line to an idle sender. The control circuits are then dismissed, dialling tone is supplied and the wanted number is dialled and registered in the sender. When the exchange code has been received, the sender seizes an originating marker (74), which controls the establishment of the connection to an idle outgoing trunk circuit to the wanted exchange in known manner, the marker then controlling the selection of the wanted line also in known manner. Non-numerical switching. Line relay L0- 69 (21) operates to the calling subscriber's loop, to earth conductors 2105, 2106 to identify the calling line to the frame control circuit. For each level or group of the switch frame in which a line is calling, a group start relay HA0-9 (24) (not shown) operates, and the frame control circuit (25, 26) prefers one level to energize the related horizontal group relay HG0-9, say HG0 (22), which prepares the links relating to the selected level by operating the corresponding select magnets SLS0 (16, 19, 22) in the secondary line cross-bar switches to which the links extend. The selected group relay HG0 also extends the conductor 2105 to a vertical row preference circuit (31) in which, after a relay H0 (21) has broken the multiple connection between the start leads of the switches of the selected level, relays V0-6 (31) are left energized corresponding to the vertical rows in which there are calling lines. The relays V0-6 control a'preference circuit to select one vertical row to be served, the corresponding relay VC0-6 (24) operating to help identify the calling line to the recorder at a later stage. The selection circuit also operates relays, say HM0, LR0 (21), individual to the selected group of ten lines. Relay LR0 extends the conductor 2106 and the control circuit to a line preference circuit comprising relays LT0-9 (32), which finally selects the line to be served. Selection of available district junctor group and sub-group. The selected line group relay LR0 (21) causes the district frame preference circuit to test five district frames and select one which has one or more idle district junctors available to the selected switch, an idle sender link control circuit, and access to an idle sender through an idle sender link. A first test is for a junctor group with at least two idle district junctors, a reserve test such as described in Specification 530,085 for a group with a single idle junctor being made if the first test fails. First test. Operation of the selected horizontal group relay HG00 (22) connects battery to the windings of test relays T0-T9 (34) relating to a group of ten line links connecting the primary and secondary line switches, those links already connected to district or line junctors operating the related test relays, the relays corresponding to idle links remaining normal. Associated with ten sub-groups of ten district junctors connecting the calling line switch frames with five district frames are ten test relays arranged in pairs G0, G1 ... G8, G9 (33). These test relays each have an energizing circuit including the back contacts of the related line link test relays T0-9 (34), sub-group test relays CA, CB (45), group busy relay DP (45), and ten branches over the back contacts of relays GB0-9 (46) and SSH0ASSH9A (37) or SSH0B-SSH9B (40). Only those relays G0-9 (33) operate where (1) the related line link test relay T0-9 (34) is normal, indicating that the line link is idle, (2) the related marginal test relay CA or CB referred to later under the heading " Availability of district junctor group " is normal, indicating that there are at least two idle district junctors in the related sub-group, (3) the group busy relay DP is normal to indicate that the sender link control circuit is idle, (4) at least of one the relays GB0-9 is normal to indicate that the related junctor has access to an idle sender, and (5) that at least one of the hold magnets SSH0A-SSH9A or SSH0B-SSH9B is normal to indicate that the associated sender link is idle. Each group of twenty district junctors is represented by a lock-out relay D0-D4 (30) at each line link frame having access to the group, these relays being arranged in a chain circuit so that operation of the selected subgroup test relay G0-9 (33) in combination with a preference circuit including relays PR, RP (33), and varied according to which line link frame is calling, results in the selection of one of the groups of district junctors and the operation of its lock-out relay in the appropriate line link frame. The selected lock-out relay locks _up and signals the sender link control circuit associated with the preferred district junctor group for an extension by operating the related district group preference relay GP0-4 (41) individual to the group of trunks associated with the line switch frame. The operating circuits of these preference relays are arranged in a chain, so that, if more than one line switch frame desires service, preference is given to the highest numbered relay. The selected district group preference relay, say GP0, operates a district group relay G (45) which locks up the selected sub-group test relay, say G0 (33), and according to whether this is odd or even-numbered, so relay DB0 or DAO (30) energizes, and in combination with the selected lock-out relay DO (30) establishes a number of circuits interconnecting the line link control circuit with the sender link control circuit associated with the selected subgroup of district junctors. The selection of the sub-groups of district junctors determines which secondary line switch (22) will be used and therefore which of the ten line links serving the calling line will be used, relay DA0 in the example operating the primary select magnet PLS0-60 (21) in the cross-bar switch associated with that line link. Selection of idle district junctor. Operation of relay DA0 or DB0 (30) energizes the related sub-group relay BA or BB (45), and the selected group preference relay GP0 operates relays RS, DE (44). District group relay G operates relay ON (44) to release the selected group preference relay GP0 and operate group busy relay DP (45) to mark the sender link control circuit busy. Relays ON (44), DE and BA or BB apply earth to the windings of relays D0-9 (44) individual to the junctors of the sub-group, battery being applied to the other side through a resistance 7000 by each idle district junctor, whereby those relays D0-9 operate which correspond to idle district junctors in the selected sub-group, to operate relay DS (47) over the normal contacts of the relay BA or BB individual to the other subgroup, as a check that only one of the subgroup relays BA, BB has energized. Relay DS operates relays CA, CB (45). If more than one district junctor is idle, a relay TM (44) energizes and one junctor is selected by a