Patent GB-191512673-A (GB)
Title: Improvements in Automatic Telephone Systems.
Filed: 1915-09-03
Abstract: 12,673. Relay Automatic Telephone Co., [Assignees of Betulander, G. A.]. Nov. 17 1914, [Convention date]. Automatic exchange systems; impulse-transmitters.-Relates tosystems of the kind in which numerical selectors are used temporarily for establishing connexions, the selector, as soon as a connexion has been completed, disengaging itself from the trunk in use and putting itself in readiness for another call. In order to reduce the period during which a selector is engaged for any call, and therefore the number of selectors required for a group of trunks, a calling-trunk is not marked as calling in in its relation to the selector until the subscriber has operated the dial of his impulsesender, and preferably not until the dial has been released after setting. The invention is described as applied to a system in which the impulse-transmitters are retained after setting until released electromagnetically from the exchange, and in which relay sets are used as numerical selectors. Construction of impulse transmitter. The disk 1 has teeth 2 for operating the impulsecontact 3, 4, and ratchet teeth 5 for engaging a pawl 7 controlled by a magnet 6. A catch 8 retains the pawl in its attracted position until tripped by a pin 9 when the disk reaches its normal position. During the setting movement of the disk, the contact 21 is opened and contacts 45, 46 closed, contact 45 connecting the magnet 6 to line, and contact 46 short-circuiting the line during the forward movement of the disk. At the end of the setting movement, the spring 3 rests on the top of a tooth 2, contact 3, 4 being open, and the point of pawl 7 lies between two teeth 5. When the subscriber releases the disk, contact 46 is broken, so that the line circuit is momentarily opened until the disk is turned back half a tooth by its spring and the line circuit closed at contact 3, 4. This momentary interruption serves to mark the trunk as calling in its relation to the selector. Connexion of calling-line to selector. When a calling-subscriber removes his receiver, his line relay 23 is energized over circuit a and brings about the connexion of his line by relays 30, 31 in known manner to an idle trunk 24, 25. The relay 33 of this trunk is energized over the calling-line and energizes a slow-release relay 35 which closes a circuit d for the subscriber's cut-off relay 36 and relays 30, 31, and a circuit e for a relay 41 individual to the trunk 24, 25, thus preparing circuits for the relays 43, 44 which control the connexion of the trunk 24, 25 to the selector S. When the subscriber has set and released the dial of his impulse-transmitter, the line circuit is momentarily broken as described above, and the relay 33 closes a circuit f for relay 49, and a circuit g for relay 44. The relay 49 locks up over circuit h and prepares a circuit n for a relay 52. The relay 44 locks up over a circuit i and prepares a circuit k for the selector-connecting relay 43. The circuit k includes, in series, the back contacts of the corresponding relays 43<1> of other trunks, such as 24<1>, 25<1>, so that as long as the selector S is connected to any such trunk, the relay 43<1> of which is therefore energized, the circuit k of a calling- trunk will not be completed. If, or as soon as, the selector S is free, the relay 43 is energized over circuit k, locks up over circuit l, opens the energizing-circuits of the relays, such as 43<1>, of all the other trunks having access to the selector S, and completes a circuit n for the selector impulse relay 14, and the relay 52, which opens the locking-circuit h of relay 49 and short-circuits a resistance 32, thus strengthening the line current sufficiently to cause the magnet 6 to release the impulse transmitter. Operation of selector. The selector comprises a series of ten primary relays 10 and ten auxiliary relays 11, the relays 10 being all energized when the selector-connecting relay 43 is energized. One of the relays 11 is energized and the corresponding relay 10 de-energized for each selecting-impulse. The relay 14, energized over circuit n as describd above, closes circuit o for a slow-release relay 12, which attracts the armatures to prepare circuits p, q, r for the relays 13, 11. At the first interruption of the line circuit after the release of the impulse-transmitter, the relay 33 opens circuit n of relay 14, which closes (1) a holding-circuit for relay 12, (2) a circuit p for the self-locking relay 13, and (3) a circuit q, q<1> q for the first relay 11, which locks up and opens the circuit m of the corresponding relay 10, so that this de-energises as soon as'the relay 14 is again energized. Further impulses act in a similar manner on the relays 10, 11 ; but as soon as the impulses cease, relay 12 is de-energized and closes a circuit s over the back contacts of all the de-energized relays 10 and the the front contacts of the energized relays 10. This circuit operates in the manner described in Specification 6210/14 to effect the testing of the trunks belonging to the selected group and then to close the circuit of a connecting-relay 40 by which trunk 24, 25 is connected to an idle trunk 87, 88 in the selected group, and circuit e of the relay 41 is opened, thus de-energizing the relays 43, 44 and releasing the selector S. During the operation of the selector S, the relay 49 is kept energized over circuit f; but when the interruptions of the line circuit cease, the relay 49 de-energizes and opens the circuit of relay 52, so that both these relays are restored to their normal conditions.