Patent GB-422644-A (GB)
Title: Improvements relating to automatic telephone and like selective systems
IPC: H04M3/523
Filed: 1933-11-13
Abstract: 422,644. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and DIXON, R. G., 162, Westmount Road, Eltham Park, both in London. Nov. 13, 1933, No. 31576. [Class 40 (iv)] An allotter which gives access to several groups, on being released after completing its function, hunts in a particular group, e.g. that in which it has just previously made an allotment or a preferred group whether its services are immediately required or not. In the system described, which resembles that described in Specification 415,225, a primary allotter gives access to four groups of regular finders over the first half of its bank and to corresponding groups of overflow finders, which are only made available when the allotter has passed in a continuous movement over all the regular finders, in the second half. The overflow finders extend connection to the banks of secondary finders which are controlled by a similar allotter. Primary allotter. Four pairs of start wires YZ, WX, one for each of four two-hundred line groups enter the start circuit shown in part in Fig. 2, this circuit being common to four allotters. Each allotter is first-choice to a different group, that shown in Fig. 3 being first-choice to the group to which the wires YZ, WX belong. The line relay L of a calling subscriber in this group grounds YZ or WX to indicate the half of the group to which he belongs and, if the first choice-allotter is idle and its relay PJA therefore is operated, marking relay A or E pulls up. A call from another group would operate one of a number of marking relays (not shown) controlling contacts aa, ee. Following the operation of a marking relay, PS is energized either alone or with either or both of relays PX, PW. PX if operated energizes PG, PGA to switch over from the even to the odd-numbered allotter wipers. PS releases PJA to extend the start circuit, energizes PB to connect up the latch magnet PALM and marks the proper group of finders over wiper PAS15 or PAS16. If the allotter is on or when it reaches the terminals of an idle finder in the group, PC releases the latch magnet and PCA, PD pull up. PD locks up and PC, PCA fall back when ground is returned from the group selector. On the operation of PE to stop the finder PF pulls up, locks, holds the marking relay, operates the finder switching relay and disconnects PB(i) but removes a shunt from PB(ii) to enable the relay to hold temporarily in series with PE. PE, PB(ii) are, however, short-circuited by the finder switching relay whereupon PD, PF fall back and make a temporary circuit for PH which locks up, holds the marking relay and energizes PM and the allotter latch magnet. If an idle finder is encountered in the group still being marked, PC stops the allotter and the circuit is restored to normal since PM has already released PS and is itself released when PCA unlocks PH. If no idle finder is found in the marked group the allotter is stopped in the normal position shown by the battery connection over pm6. If in hunting the allotter passes through its normal position or if it starts from that position, PT pulls up, holds itself and energizes PU which adds the overflow to the regular finders marked over wipers PAS15 and PAS16. When now the allotter passes the terminal separating the regular from the overflow finders, PP pulls up and locks so that when PD pulls up on the seizure of an available overflow finder, PQ is included in its locking circuit and connects PM to one or other of the wires AM to mark the finder in the banks of the secondary finders. Primary and secondary finders then hunt together and when PM and PF are both operated, PB, PS, PC, PCA, PT, PU, PD, PQ, PP, PE, PF are released and the allotter goes home. Secondary finders are marked unavailable even if idle by the operation of GP when all the secondary finders giving access to them are busy. If the allotter is unsuccessful in a hunt through the overflow finders it is brought to rest temporarily on its penultimate or last terminals, according to the marking connections to banks PAS15 and PAS16, PL operating in series with the test relay. PP in this case operates one of four overflow meters. PL connects up common apparatus IS which causes spc to be closed for half a second every four seconds. When spc closes, PC, PCA are shunted out and release PD, PB, PT, PU. When spc opens again PL falls and PB is re-operated and the allotter goes over its bank again. This operation is repeated indefinitely until a finder is allotted. Control of regular and overflow finders. PD in the allotter energizes the latch magnet PFLM and completes the test circuit over relay PE and one of the wipers P, Fig. 4, the particular one connected depending on the condition of PW. At the same time a circuit is made over OLR for an additional winding on the group selector line relay which causes ground to be connected to the private wire. When the finder is stopped the appropriate switching relay HA or HB is operated from the allotter. Cut-off relay K is operated over the metering wire and locks up over wiper P. The overflow finder is controlled in the same way except that there is no switching relay, a battery-connected relay being connected to one of the wires AM to control wiper selection in the primary finder by a marking in the secondary finder banks. Secondary allotter. A starting wire STL enters the circuit shown in Fig. 6 for each of six groups of primary finders, a group in this case meaning the finders accessible to a particular group of secondary finders, and four allotters are controlled by this start circuit. When a primary allotter seizes an overflow finder its relay PD connects battery over a resistance to the appropriate wire STL and if the allotter shown is idle and its relay SJA therefore is operated the marking relay SA pulls up and energizes the wiper changing relay SW and relay SS which releases SJA. A call from another group would have energized one of a number of marking relays (not shown) having contacts saa, see and arranged in some cases to energize SS without SW. If a second call arrives over the same starting wire the marginal relay ST energizes a marking relay over the lower chain circuit. SS also energizes SN which is followed by SP, SQ, SZ and the latch magnet SALM if necessary. The switch is stopped on a finder in the marked group by SU which is followed by STA, SR to initiate control of the secondary finder and operate the group selector line relay. Ground returned from the group selector energizes GF to release STA, SU. SK which operates to stop the finder is followed by SKA, SL, SM. SM grounds CE to mark the overflow finder busy after the release of the primary allotter, which takes place as soon as the secondary finder stops, pending the operation of the finder switching relay H. On the release of the primary allotter SK, SKA, SL, SM fall back and also SA, SS, SR. Control of secondary finder. Operation of SR in the allotter energizes the latch magnet SFLM which is released by SK when the calling overflow finder is reached. When the group selector returns ground, SM in the allotter energizes and on the relapse of SL when the primary allotter is released the switching relay H pulls up and locks the private wire. Irregular operation. When the secondary allotter is taken into use, SN, SP, SQ pull up and then fall back in succession unless the release of SQ is prevented by the operation of SL when the secondary finder stops. If SQ does fall back, SM is operated and releases SS and the marking relay and a homing circuit is made for the allotter over a contact of the offnormal relay SX. Since SJA is not operated the starting circuit is thus extended to another allotter. Standstill release and fault alarm. PB which is operated when the primary allotter is taken into use connects PA to a pulse wire SPW and PA on operation locks and connects PZ to a pulse wire ZPW. Normally PA is unlocked, e.g. by the operation of PF before PZ can operate, but in case of a fault PZ locks up, gives alarms, releases PA, PB and disconnects PJA to hold the allotter out of service. The seized primary finder is released by the relapse of PB. CL which is common to the four allotters available to the pair of start circuits shown and is operated if all four allotters are faulty, releases all the relays PZ. Premature release. If a subscriber clears before his line is found the primary finder is stopped on a circuit over a chain a6 .. d6 or e6 .. h6 involving contacts of the marking relays of the start circuit. Similar means are provided for the secondary finders. Routine testing. A test key is provided for each pair of starting wires, that marked RTK belonging to the pair YZ, WX. The keys connect a grounded common relay RS to either of their associated start wires. RS marks a particular position in the finders. The finders are thus driven in succession to that position and are then released, since the group selectors find no holding loop, unless plugs have been inserted in their test jacks, Fig. 9. If a call arrives during the test, the starting ground shunts out RS to remove the test-marking condition from the finders. Normally only regular finders would be operated in this way, and to bring in the overflow finders a key SCC is actuated to operate relay RT individual to the key. RT holds PU continuously after PT has once operated and the allotters therefore allot regular and overflow finders indiscriminately. The secondary finders can be tested independently of the primary finders by means of test keys such as RTS which put strong or weak battery according to the condition of DCK on the associated starting wire and at the same time mark a position in one or other of the banks of the finders according to the condition of key WSK, by connecting it to SRM. When a finder stops in this position, SRM energizes SRR which locks over CE and releases SRM and SK in the allotter. On the release of SK, H switches the f