Patent GB-261464-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/60
Filed: 1925-08-17
Abstract: 261,464. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), (Polinkowsky, L.). Aug. 17, 1925. Semi-automatic exchange systems. - An operators' trunk circuit at which a keyboard equipment may be associated with a manual-toautomatic trunk is so arranged that by small changes of wiring it is adapted to be included in the trunk either at the manual end or at the automatic end or at an intermediate point. If at either exchange, a two-wire trunk extends to the distant exchange and a three-wire trunk to the local apparatus, whilst if at an intermediate point, a two-wire trunk extends in each direction. In the circuit shown in Fig. 1, the full-line connections are used when the operator's circuit is at an intermediate point. When at the manual end, the, connections marked with a cross are removed and the dotted connections XX, XX<1> added. When at the automatic end, the connections marked with a cross are again removed and the dotted connections XX<1>, XX<2> are added. In all cases, a keyboard equipment. Figs. 2, 3, is associated with the trunk circuit over a finder TF and means may be provided for concentrating calls so that an operator may assign trunks associated with a neighbouring position and set up the call on the keyboard at her own position. The arrangement at the keyboard is such that a wanted number may be registered and the common keyboard released even if the trunkfinder has not yet completed its operation. Office keys may be provided as shown in dotted lines in Figs. 2, 3, each key controlling the operation of a single relay which determines the transmission of one or two extra digits to route the call over more than one exchange. Trunk-finder TF: concentrating calls. The depression of an assignment key Ask energizes relay Asr which lights lamp GL and locks in series with relay Bsr, the latter completing a circuit over jack BJ and cam B for driving sequence switch R of the next idle register into its 3rd position. The finder power-magnet P is now energized and the brushes a - - e are rotated until a circuit is completed over a front contact of relay Asr, brush c, cam F, relay Tr, cam G and brush e to earth, The test relay Tr locks up in series with relay Shr which, when the number registration is complete, drives the switch R to its 5th position in which lamp BL is flashed over interrupter I. The trunks at an adjacent position D (in the top right-hand corner of Fig. 2) are multipled in the bank of the finder TF but are not normally selectable owing to the absence of earth on the terminals in the bank of wiper e. These may however, be rendered selectable when it is desired to concentrate calls, by the depression at the adjacent position of an order-wire key which placesearth on the terminals of the e-bank. Setting of keyboard. The operation of the number keys causes the wanted number to be registered on relays Mnr - - Unr. It will be observed that for the thousands, hundreds and tens digits, only one register relay is provided for' two adjacent digits e.g. for digits 8 and 9. Discrimination between two such digits is effected by relays Mer - - Der which are energized for the smaller of the two digits and at the appropriatetime effect the operation of relay Tkr which causes one pair of counting relays Scr1, Tcr1 to be skipped. When a complete set of four keys has been depressed, a series circuit is completed over cams J, M and contacts of the register relays for a. relay Clr which locks up the register relays and moves the switch R into its 4th position. The keyboard is now disconnected at cam N and may be used for another call even if the finder TF is still hunting. Control of selectors. If office keys are not provided, a circuit is completed over cam S in the 5th position of the switch R for relays Tnr, Trr which close a circuit over cam D for moving the switch to its 6th position in which it energizes further over cam C and moves to position 7. Further movement similarly takes place to position 9 in which the front contact of the outstepping relay Osr is connected over cams Q, R and contacts of the thousands register relays to the appropriate position in the counting chain. Selection takes place as usual and when relays Tnr, Trr operate the switch R moves to its 10th position in which hunting takes place. At this time relays Sfr, Slr, Kcr operate but the release .of relay Osr at the conclusion of hunting releases relays Sfr, Kcr and the switch R moves to its 11th position in which hundreds selection takes place in a similar manner. The switch R does not move out of its 12th position to initiate tens selection until the A-operator has plugged into the assigned trunk, this operation causing the energization of relays Bgr, Lgr and marginal relay Mgr. Tens and units selection proceed in known manner and switch R then moves to its 18th position in which it waits, unless the other registers B, C of the position are both busy in which case it will move to its 1st position over its own cam C, cam O of register B, and cam K of register C. In passing the 16th and 17th positions, low resistance battery is connected over cam F and wiper c to release relay Asr. Provision of office keys. If these are provided, the connections marked with a cross in Figs. 2, 3 are removed and the dotted connections in these Figures are inserted. A single register relay Cdr is provided for each office, the left-hand contacts of this relay being suitably wired over - a distributing frame to the conductors leading to the counting chain so that normally two additional selections take place in positions 5 and 7. Relays Sor. Str are also provided and are suitably wired to the contacts of the office relays to suppress one or both office-selecting stages if desired. With relay Str operated, selection takes place in the 5th position but in the 7th position, relay Trr operates over the upper outer contact of cam S and moves the switch R on to its 9th position. If relay Sor is energized, relay Trr operates in the 5th position of the switch and both selecting stages are omitted. Supervision of completed call. With the operator's circuit at an intermediate position as shown in full lines, the release of relay Asr closes a momentary circuit for relay Ctr which locks up over front contacts of relay Lgr and completes the talking connection. The operation of relay Srr when the called subscriber replies gives supervision to the A-operator. If the semi-automatic operator is at either the manual or the automatic exchange, relay Ctr remains operated over front contacts of relay Lhr which locks to the third wire.