Patent GB-366469-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1930-10-02
Abstract: 366,469. Automatic exchange systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, BEALE, C. E., 59, Towers Road, and TAYLOR, R., 30, Oulton Road, both in Wavertree, all in Liverpool. Oct. 2, 1930, Nos. 29568 and 33979. [Class 40 (iv).] The relay for associating a switch or repeater with a common control circuit is energized over the calling loop in series with the line relay in the common circuit. The invention is described with reference to up and around switches acting as group and final selectors and in some cases with two sets of wipers and to an impulse repeater. Figs. 1 and 2 of the second Provisional Specification and referred to for convenience hereinafter as Figs. 7 and 8, show a discriminating selector repeater for co-operation with a main office using switches of the above kind. The common equipment is associated with a vertical instead of a horizontal row of switches so that a shelf of ten switches has access to ten different common circuits. Double hunting first selector, Fig. 1. As soon as the link is taken into use, 2A, 2B in the common circuit are operated, and when the finder switches through, 2K is cut into the circuit of 2A and locks up. The digit is repeated to magnet 2VM by 2A through 2C which at the end of the digit initiates interaction in known manner between the rotary magnet 2RM and 2G until if 3e finds an idle trunk 2G is unable to re-operate and 2HA switches through, or if 6e alone finds an idle trunk 2G pulls up and locks itself and 2HB switches through. Outgoing repeater, Fig. 6. When the repeater is seized, 6K, AC are operated in series over the calling loop followed by BC which busies the repeaters. Battery is now connected over the upper junction wire to energize the K relay of the incoming selector. The latter connects battery over the common line relay to the lower junction wire, energizing IC which energizes IX. IX locks, connects IC, D across the loop and energizes 2J, JR. In all the other repeaters corresponding to the same control circuit at the incoming end JB is operated to mark them busy. AC repeats the digits, 7C short-circuiting the inductive part of the bridge after the first impulse. Ringing tone goes back via QC. When the called party replies, 3D releases 2J, JR. 8B pulls up, connects up the feed relay 8A and releases the common equipment, and I, 4D pull up over the called loop. When the call is released BC is energized temporarily to hold the repeaters busy until the distant switches have been released. With this arrangement, the impulse relay since it is not on the line during conversation is of low impedance. Incoming and second selectors. These may be of the double hunting type described above, the strap X being removed and the strap Y added for the incoming selector. A simplified 100-point selector is described with reference to Fig. 2 (not shown). 200-line final selector, Fig. 3. This is selectable over either of two levels, 4A being operated in series with 4K or WS, the latter operating 4K. 4B, 4C follow. The tens digit goes to 4VM and at the end of the train 4C falls energizing E to prepare the rotary magnet 4RM for the final digit and then pulls up again. The first impulse of this digit energizes RN which locks up. At the end of the digit 4C and E fall in succession. If the line is idle the relapse of 4C energizes 3H which at once locks over its light armature 3h1 and when E falls the ringing and ring back tone circuits are made over F, 4A and J is energized. When the subscriber replies, F pulls up a light armature f1 and then operates fully in a local circuit, energizes D over the called loop and releases J. RN then falls and energizes release relay 5B in the individual circuit. Line relay 5A then pulls up over the calling loop, and holds 5B and the common equipment is released. If the wanted line i busy 3H does not pull up and busy tone and flash go back from 2BF. P.B.X. final selector, Figs. 4 and 5. In one set of banks the switch makes connections with ordinary lines in the same way as that shown in Fig. 3. Associated with the other set is an additional bank PA in which all the lines of a group except the last are grounded. If the first line of such a group is dialled, HS is operated when 6C falls and assuming the line to be busy, the relapse of 1E makes a circuit for the rctary magnet in series with 6C, HS. When the magnet has operated, 1E pulls up again, releasing the magnet and this interaction continues until an idle line is found in which case 4H stops the hunt and prepares the ringing circuit, or the end of the group is reached in which case HS will fall allowing 1J to operate on the relapse of E and send the busy signal. If a line other than the first is called, HS being short-circuited by the wipers 1f, 2f, the switch behaves as an ordinary final selector. All trunks busy. If all the trunks tested by the first selector, Fig. 1, are busy, eleventh step springs cs operate BB and an overflow meter, and busy flash is sent back from BF, 2B being held at BH while the line relay is short-circuited. Similar arrangements are provided in the second and final selectors. If busy flash is received by the repeater, Fig. 6, IC falls releasing IX at the first flash impulse. On re-operating, IC energizes 2BB which connects up a local busy flash supply and opens the loop to release the distant switches. Irregular operations. If a subscriber fails to dial, S and Z relays TP, TZ in the first selector control circuit give the selector one vertical step and it then hunts on the first level for a free NU tone equipment. Similar arrangements may be provided in incoming selectors. If a spare number is dialled, the final selector is set to an NU tone equipment and battery on the upper wire energizes the ring trip relay F. D, however, is not operated. J and RN fall in turn to release the common equipment and switch the line through to the tone equipment. If the calling party in the satellite system, Figs. 7 and 8, fails to dial or if he fails to clear a delayed alarm (not shown) is operated in series with LP. Calls to manual boards. 2LR, Fig. 6, operates over the calling loop to ground on the c wire, locks and sends back ringing tone over QR and is cut off by 2CO when the operator plugs in. During the release period of 2LR ringing current is connected to the line to operate MO in the repeater. The latter locks and energizes 8B to cause the repeater to switch through and to release the common equipment. Discriminating selector repeater, Figs. 7 and 8. When the calling line is switched through, A, B, MD, J are operated and JFS is driven to an idle junction under control of K which on operating connects battery to the lower junction wire to energize the K relay of the distant incoming selector. The latter sends back battery over the common impulse relay and the upper junction wire to operate I, and ground over the corresponding wire of all the other junctions to operate their relays JB and so mark them busy at the outgoing end. I energizes IX which locks and bridges the junction, removing the battery connection from the lower wire. Dialling signal which is normally received from the main office, is sent if all junctions are busy from the last terminals of JFS. A repeats the digits over the junctions and to the vertical magnet VM of the discriminating selector and parallel dialling relay C which short-circuits the inductance of the bridge. At the first impulse JG is energized and locks up and when the switch goes off normal, G is energized and locks up. At the end of the digit the relapse of C gives the rotary magnet RM a single impulse. The terminal now engaged by 2P is connected to one of the points c, f, b, a, e over a frame CCF. A connection to a or b indicates a main office call and JD is operated and locks, cuts off G and JG, opens the impulsing circuit to the vertical magnet, and sends a busy signal if necessary. A connection to c causes the operation of DA and thus of the release magnet. DA remains locked but OA is operated and locked to cut off the release magnet when the switch reaches normal and to change the connections of the points a .. f for the second digit. If connection is made with e after the first digit LD is energized indicating a local call, the test relay H is connected to wiper 1P, K is released to free the junction which is guarded temporarily during the release time of JG and then, during the release time of JB, to give time for release in the main exchange. LD is followed by G which interacts with the rotary magnet until an idle local trunk is engaged, whereupon H switches through. On release of a main office call JA, JB come into play as described above. If the subscriber hangs up during a flash period, release is delayed by the operation of I and consequent holding of MD when B falls. Metering. When the called party replies in a local call at a main office, D in the final selector common control circuit, Fig. 3, is energized and connects up booster battery and J is released and releases RN which cuts it off. In an inter-office call corresponding functions are exercised by the common relays 3D, 2J, JR, Fig. 6, controlling the outgoing repeater. This action is prevented in the case of calls to a manual board in which case MO is energized to cause the switch through as previously described, and not 3D. In the discriminating selector repeater, Figs. 7 and 8, booster battery is connected up by the relapse of MD which is released by the supervisory relay D and cut off by the release of J which follows that of MD. Preventing metering-operator hold arrangement, Figs. 7 and 8. In zero calls MD is held over post springs NP to prevent metering. When the calling party clears, A, D, B fall and C pulls up to guard the switch. Holding battery on the lower talking wire re-energizes I which re-operates MP to hold C until the operator clears.