Patent GB-400733-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04M3/523
Filed: 1932-07-18
Abstract: 400,733. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Tothill Street, and PATTERSON, W. G., 59, Grove Park Road, Mottingham, both in London. July 18, 1932, No. 20339. [Class 40 (iv).] A 50-point or 100-point high-speed switch driven by an individual electric motor is employed as an allotting-switch for callfinders and is associated with a plurality of groups of finders allotting one in any required group as the occasion arises. In the system shown, both the finders and the allotters are switches of the kind described in Specification 388,173. Specification 381,995 also is referred to. General arrangement of allotters and finders. Each finder, Fig. 1, has access to 200 lines arranged in four sub-groups W .. Z accessible to two sets of double-ended wipers. Four allotters AS1 .. AS4 are associated in common with a plurality of groups of finders, the allotters being respectively first choice to calls in the sub-groups W.. Z, but each capable of dealing with calls in any sub-group. All the finders of a group, some of which may be linked individually to a group selector (ungraded finders) whilst others share a group selector (graded finders), are connected consecutively in the allotter banks and the allotter is arranged to rest normally at the beginning of a group, moving forward after use to the beginning of the next group ahead. The ungraded finders are all connected at the beginning of a group so that they will always be selected in preference to the graded finders, it being arranged that if at the end of a call there is still a calling signal in the same sub-group the allotter is only able to allot a new finder without proceeding to a normal position if the previouslyused finder is an ungraded one. When an allotter is idle, a relay P .. S is energized, extending each of the sub-group starting wires W .. Z, Fig. 3, over winding (i) of one of a group of relays such as AP .. AS and a corresponding lead S1 .. S4 to a relay SS in the first idle allotter. Allotment and control of individual finder. When a line (in sub-group W, say) initiates a call, ground on wire W energizes relay AP which locks over winding (ii) and battery on lead H1 in the allotter, and connects direct ground to lead S1 to operate SS over a normal contact of allotter wiper 8. SS energizes relay B which operates the latch magnet ALM. Contact ap3 marks in allotter bank 7 the group of finders which has access to the calling line and when an idle one is reached (denoted by battery on the wire p of the associated group selector) relays T, TA operate over banks 7, 6. Relay TA connects up the latch magnet FLM of the allotted finder over wiper 3 and the test relay TB over wiper 1, and when the calling line is found TB operates and connects earth over rectifier R2 to operate the cut-off relay K, the resistance of the rectifier being sufficient to prevent TB from being short-circuited. Relay TC also operates connecting ground over wiper 4 to operate switching relay HA. At the same time relay B is released and SS also having been released by the disconnection of the line relay L the allotter is driven over contacts ON1 to a normal position at the beginning of the next group. If another line in the same subgroup is calling and the allotter is resting amongst the ungraded finders relay SS remains locked over wiper 8 and a multipled connection x so that another ungraded finder is allotted. If, however, the previously-used finder was graded relay SS is unable to remain looked over multiple connection y owing to the operation of TC and the allotter therefore goes right round its bank and tests against the ungraded finders of the group. When a line in either of the subgroups Y, Z calls, relay SW operates in series with SS switching over the testing circuit from wiper 1 to wiper 2 and causing switching relay HB to operate instead of HA. If all allotters are busy when a call is made, ground on the starting-wire operates meter AOM. All finders of a group busy. When the last finder of a group is reached and found busy, relay LC operates over wiper 6, stopping the allotter and connecting ground to lead PS to start an impulsing device which periodically grounds lead EP. Relays T, TA are shortcircuited at the first pulse, SS, B releases, and at the end of the pulse LC also releases and the allotter moves to the next normal position. An overflow meter FOM is operated over wiper 3. Faulty finder. If an allotted finder does not find a calling line within a definite time, thermostat TH operates fault relay F and lamp AL, the relay F causing the allotter to remain associated with the faulty finder.