Patent GB-191509283-A (GB)
Title: Improvements in Automatic or Semi-automatic Telephone Systems.
Filed: 1915-06-24
Abstract: 9283. Relay Automatic Telephone Co., [Betulander, G. A.]. June 24. Automatic exchange systems; impulse - transmitters. - In systems in which the setting of the selectors is effected by means of electromagnetically-controlled number switches without the use of any earth connexion, the setting of the selectors is controlled by an impulse relay included in the loop circuit and responsive to variations in current caused by the number switch, these variations of current being different from those which control the number switch. The impulse relay is preferably operated through interruptions of the line current, while the oontrolling-magnet of the number switch is operated. by varying the strength of the line current; in such a system, the number switch and the selector exercise a reciprocal control over each other. In modifications, the number switch is released by a strengthening of the line current or by an interruption in the line current, and then sends in the impulses in the usual way without any further control. The invention is described as applied to the control of a selector consisting of a group of relays, which is common to a group of lines, being temporarily connected to a calling-line and detached therefrom as soon as the desired connexion is established. Such a selector is described in Specification 6210/14. First arrangement, Fig. 1, in which the number switch sets the selector by interruptions of the line circuit, and is returned step by step to its normal position by impulses of strengthened current sent back bv the selector. The number switch consists of disk 1 having teeth 2 operating an impulse contact 3, 4, and teeth 5 engaged by an escapement pawl 7 controlled by a magnet 6. In any off-normal position of the disk, the contact 26 is opened and contact 41 closed. When a subscriber removes his receiver, he is connected by means not shown to an idle junction 16, 17, the connecting-relay 20 and a relay 21 being initially energized by circuits also not shown. The impulse relay 25 is thus energized over the circuit a and closes a. holding-circuit b for relay 21 and an energizing-circuit c for a slow-release relay 30, which closes a holding-circuit d for relay 20 and a circuit e for a relay 35, which prepares a circuit F for a relay 37 controlling the association of the relay selector with the calling-line. As the selector is assigned in common to a number of junction lines 16, 17, a succession device is provided to control contacts 38 included in the circuits of the relays 37 assigned to the different junction lines in such a manner that only one subscriber at a time can be connected to the selector. If, or as soon as, the selector is free, the relay 37 is energized and the wire 16 connected to the impulse relay 39 of the selector. At the same time, battery is connected over circuits f to all the auxiliary relays 8, which are thus energized. The above operations all take place as the result of the removal of the calling-subscriber's receiver. During the setting of the number switch, magnet 6 is connected to the line over contact 41, but is short-circuited over a contact 42. As soon as the number switch is released, contact 42 opens, and the magnet 6 energizes over circuit A and allows the disk 1 to rotate through half a tooth, whereupon the contact 3, 4 opens the circuit of magnet 6 and impulse relay 25. The relay 25 opens the holding - circuit b of relay 21, which earths the upper winding of relay 25 through a resistance 43 instead of directly. The open-circuiting of magnet 6 allows the disk 1 to rotate another half-step, so that the contact 3, 4 is again closed, and the circuit of magnet 6 and relay 25 again closed, but this time through a circuit including the resistance 43. This current is insufficient to energize magnet 6, but relay 25 energizes. If the selector is not immediately available, the number switch, after having been turned back one tooth, is maintained in its locked position. As soon as the selector becomes idle, relay 37 completes circuit h through the selector impulserelay 39 and relay 23. The relay 23 energizes relay 21 and locks up over circuit i; the upper winding of relay 25 is now earthed through resistance 43 over circuit k, the direct connexion to earth being open at the contact of relay 23, and the current through the magnet 6 therefore remains insufficient to energize it. The relay 39 closes the circuit l of a slowrelease relay 12, which locks up over circuit m and closes circuit n for relay 11, which locks up over circuit o. The relays 39, 12 close circuit p for the first auxiliary relay 9, which locks up over circuit q maintains the first switching- relay 8 energized over circuit r, and closes circuit s through the relay 49, which opens the circuit i through relays 39, 23. The relay 39 opens circuits r, m, whereupon the first switching-relay 8 de-energizes and opens the circuit of relay 49, while the slow-release relay 12 keeps its armature attracted. The relay 23 short-circuits the resistance 43, thus increasing the line current sufficiently to energize the magnet 6, which allows the number switch to move another step, with the same result as before, the relay 23 releasing its armature to cut in resistance 43, so that the magnet 6 cannot be energized until the relay 49 is again energized by the second auxiliary relay 9. This process is repeated for each impulse, and when these cease, the relay 12 de-energizes and closes a circuit t to a switching-device (not shown), which tests the junction lines belonging to the group selected and then sends a current through a connecting-relay 34 associated with an idle junction 27, 28, by means of which the line 16, 17 is connected to this junction and the selector disconnected. Second arrangement, Fig. 2, in which the number switch and the selector work in time with an interrupter 50 at the exchange. The relays 20, 21, 25, 30 are arranged as shown in Fig. 1, but the relay 23, instead of being connected by the circuit h, Fig. 1, to the selector impulse relay, is connected by circuit H to the interrupter 50, which also sends impulses over the circuit J to the selector. The relay 23 short-circuits the resistance 43 and thus strengthens the line current to energize the magnet 6. When the number switch reaches its normal position, the relay 21 is maintained energized over circuit b by relay 25, and thus cuts off the interrupter 50. Third arrangement, Fig. 3, in which the number switch and selector reciprocally control each other as in the arrangement shown in Fig. 1. The number switch is the same as is shown in Fig. 1, except that the springs 3, 4 normally occupy another position. The relay selector is also the same as that shown in Fig. 1, except that the relays 39, 49 work differently. At the end of the setting movement of the dial, it is held in the set position as the resistance 43 is included in the line circuit. As soon as the selector is idle, relays 35, 37 are energized, and a circuit i is completed through relays 39, 23. Relay 39 energizes slow-release relay 12, which prepares the circuit N of relay 11, and circuit p of the first auxiliary relay 9. Relay 23 energizes a slowrelease relay 30 to earth the wire 32 during the sending of the impulse, and short-circuits the resistance 43, so that the magnet 6 is energized and the dial allowed to rotate half a tooth. The contact 3, 4 is then opened, so that the magnet 6 is de-energized and the dial rotates another half-tooth. The opening of the line circuit causes relay 25 to open the circuit i of relays 23, 39. When relay 39 deenergizes, it sends an impulse (1) over circuit M to keep relay 12 energized, (2) over circuit p to the first auxiliary relay 9, and (3) over circuit N to the relay 11. When the line circuit is completed, relay 2.5 closes the circuit i again, and the operation is continued until the dial reaches normal, when the relays 25, 23. 39 are energized for a longer time. Relay 12 therefore de-energizes and completes the selected circuit t as before. The speed of operation may be regnlated by making relay 23 slow - acting to a suitable degree. Fourth arrangement, Fig. 4, in which the number switch is released by a strengthening of the line current and then transmits its impulses without any electro-magnetic control. In this system, the escapement pawl 7 of the number switch has only a single tooth and is retained in its attracted position by a catch 45, which is tripped by a pin 46 when the dial returns to its normal position. After the dial is set, the magnet 6 is in circuit with the impulse relay 25 and resistance 43. As soon as the selector becomes idle, relay 23 is energized over circuit i and short-circuits the resistance 43, thus releasing the dial, so that the line circuit is repeatedly interrupted, these impulses being repeated by relay 25 over circuit i. In order that the same circuits may he used for subscriber's lines of different resistances, the value of the resistance 43 must be suitably chosen, and it may take. the form of a relay controlling contacts in parallel with those of the relay 25. Fifth arrangement, Fig. 6, in which the number switch is released from the exchange by a short interruption of the line circuit, and then transmits its impulses without any electromagnetic control. The number switch shown comprises a dial 1 rigid with a shaft 51, on which are loosely mounted two ratchet disks 53, 54. The disk 53 is rigidly secured to the impulse-wheel 52 and carries a pawl 55 engaging the disk 54, which has an arm 56 moving between two stops 57, 58 on the dial 1. The arm 56 normally engages stop 58, keeping contact 59 closed and contact 60 open. When the disk 54 moves from normal, an arm 63 opens contact 61 and closes contact 62. The dial is held in its set position by a pawl 7 engaging the disk 53. When the subscriber removes his receiver to call, he is conne