Patent GB-605049-A (GB)
Title: Electrical signalling
IPC: H04Q1/34
Filed: 1944-12-08
Abstract: 605,049. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Dec. 8, 1944, No. 24603. Convention date, Feb. 24. [Class 40 (iv)] Each digit of a number is sent as a train of impulses which are alternately positive and negative by means of a rectifier whose connections to the impulsing circuit are periodically reversed, the circuit being fed with alternating current. As described, impulses from a subscriber's dial incorporating a rectifier are received in a register-controller by a pair of polarized relays and are stored on relay registers or on register switches, the register-controller being otherwise similar to that described in Specification 628,174. The arrangement may also be used for impulsing from a register-controller to a register-controller in a distant exchange. Construction of dial, Figs. 9, 10, 11. Within the lower housing 2 is a rectifier S of the disc type mounted on a rotatable shaft 12 and carrying brushes 20a, 20b for engaging semicircular contacts 24a, 24b separated by insulation 27. In the upper housing 1, the shaft 12 is connected through gearing 23, 25, 26, 11 to a ratchet 10 loose on the shaft 4 of the finger plate 3. Mounted on the latter shaft is a segment 7 which normally rests against a stop 13 and carries a pawl 9 engaging the ratchet 10 as well as pins P1, P3 for operating off-normal springs HC and springs F, G which are opened momentarily when the finger plate leaves the normal position and when it approaches it again. During the return movement of the finger plate, the ratchet 10 is driven by the pawl 9 and alternate positive and negative impulses are generated by the rotation of the rectifier S, the contacts 24a, 24b being connected across the line wires as long as the springs F, G are closed. To ensure that the rectifier always returns to the same position in relation to these contacts, the ratchet 10 is provided with alternate long and short teeth, and as the segment 7 approaches the normal position the pawl 9 is lifted by engagement with a raised surface 14 so that it may slip over a short tooth to engage the next long one. In a modification referred to below, the springs F, G are not required. Register-controller, Fig. 4. When the calling line is picked up, relays RBR, RCR energize as described in Specification 628,174 and connect up HR, which locks over the line and operates R1R. Dialling tone is applied. Upon operation of the dial, at springs HC, F, G, Fig. 2, the line is opened momentarily and reclosed through the rectifier R, and in consequence relay HR falls back and connects A.C. to the line through polarized relays PR+, PR- in parallel. These last relays control differential relay DR, and since PR+ responds when the line is reclosed, DR is unbalanced and energizes, connecting up R3R, R4R. Relay DTR cuts off dialling tone. The impulses produced by the rotation of the rectifier R during the return movement of the dial operate PR -, PR+ alternately, DR remaining unbalanced, and are registered on a relay chain CR2 ... 10. At the end of the train when the line is opened at springs F, G, both relays PR+, PR - are inoperative, so that DR, R3R, R4R fall back, and the first digit is transferred to the first group of storage relays XR1 ... 4. Subsequent digits set further groups of storage relays in a similar manner. The selectors may be controlled by the method of potential comparison as described in the prior Specification. A modification is described, Fig. 7 (not shown), in which the impulses are registered on digit switches connected up in turn by an in-control switch. Register-controller, Fig. 6. In this case, A.C. is applied to the calling line as soon as it is picked up, and the springs F, G are not required in the dial and the off-normal springs HC are adjusted to change over during the return movement as the. first finger hole passes the stop. Relay PR - energizes on account of rectifier S in series therewith and connects up differential relay DR, followed by R3R, R4R. When the dial is moved off-normal, the rectifier R is inserted in the line, with the result that PR + energizes in place of PR - and connects up the first counting relay CR1. The impulses generated during the return movement of the dial operate PR-, PR+ alternately and are registered on relays CR2 ... 10 as before. The digit is terminated by the change-over of the off-normal springs, when the rectifier R is cut out and both relays PR+, PR - are inoperative (rectifier S being now short-circuited) so that DR, R3R, R4R fall back to prepare for the next digit.