Patent GB-622969-A (GB)
Title: Improvements relating to telephone and like selective systems
IPC: H04Q3/42
Filed: 1947-01-24
Abstract: 622,969. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and LONG, D. P. Jan. 24, 1947, No. 2313. Addition to 605,131. [Class 40 (iv)] A high-speed single-motion selector of the kind disclosed in the parent Specification having a plurality of wiper sets each comprising two line wipers and a test wiper, and a marking wiper common to all the sets, the contact arcs of the several sets being divided into two or more parts which are marked in accordance with the received digit, comprises one set of double-ended wipers 3 and four sets of wipers 1, 2 which are staggered in pairs so as to traverse their respective arcs in succession, the wipers being given a preliminary movement of 180 degrees when selection in the second arc of a pair is required. A digit switch MM in a common control circuit (Fig. 2) controls marking over wiper M3, wiper switching over wiper M4, and the sending of discriminating signals over wiper M2. Six sets of arcs arranged in pairs may be used if desired. Operation. The selector may be seized in response to either of two digits, a discriminating signal being received from the preceding stage to distinguish between them. If the two digits are one odd and one even, then, when the signal (earth on the positive wire) is transmitted for even digit seizure, impulse receiving relay A operates, but relay P is short-circuited. For odd digit seizure P comes up in series with A. Relay A is followed by guard relay B, BA, BB, and dialling relay C. Direct ground is applied to the positive wire to cut P out of the loop ; the coupling relay K, which busies the selector and the control circuit, is operated ; the control circuit is disconnected from the incoming selector test wires ; and relay SA is connected to the " S pulse wire SPW of a delay alarm arrangement associated with lamp SL. On odd digit seizure, P is followed by PP and PA, and the selector magnet MU operates and drives the wipers over the arcs of set 1 to the sub-normal position, where T comes up to cut the drive. Relay PP being differential followed by T. Subsequent search in response to an impulse train is thus limited to the broken-line arcs of sets 1 and 2 and to set 3. Relay PA interchanges the marking connections from contacts 1 and 2 of arc M3, as the outlets corresponding to odd-digit seizure are in the later part of the arc. The received impulse train is repeated by A to the magnet MM and on the relapse of C, MU operates over wiper M1. If the digit received is 1 or 2, WB operates over M4, whereas for 3, 4, 5 or 6, WA comes up. Outlets corresponding to digits 1, 2 are in set 3 ; those for 3, 4 and 5, 6 in set 2 ; and those for 7, 8 and 9, 0 in set 1. The selector hunts in the group marked over M3, T operating to battery on the test wire of the first free outlet encountered. T switches TA(i) into the circuit of MU which thereupon releases ; TA operates and connects earth to the positive wire over M2 if the digit received is even. Relay H pulls up, switches through and holds any operated wiper-choosing relay. It also earths wire d to hold the selector and any subsequent selectors until the final selector switches through in cases where the feed bridge is connected prior to the selector and is not switched into circuit until after the final selector has been set, as described in Specification 378,585. Relays A, B, BA, BB, P and PA (if operated), T and TA are released, the marking switch MM homes, and the control circuit is then available for use by the free selectors which it serves, relay K being released by the relapse of B. When the calling party hangs up, relay H falls away and the selector homes. All outlets busy. The selector reaches the 52nd (overflow) contacts of the arc searched, whereupon T energizes in a circuit including the shunted windings of LC and TA(ii). Relay LC also pulls up in this circuit, connects up busy-tone and busy-flash, and operates the appropriate overflow meter over M7 or M8. The selector and the control circuit are released concurrently when the caller clears. Dead numbers. The appropriate contacts in the arcs of M5 and M6 are cross-connected to relay S, which will therefore be energized if a dead number is called. The selector drives to the overflow position where LC comes up as above, the operation of substituting NU tone and steady earth for the busy signals. Allotment of spare outlets. If outlets corresponding to one pair of digits are not required, parts of an arc may be allotted to another pair of digits by simple commoning on the arc of wiper M3. If, however, there are two groups of outlets, one being chosen if the selector is seized in response to an even digit and the other if in response to an odd digit, it may be required that the outlets in one group corresponding to one pair of received digits shall occupy a whole arc, and that another pair of received digits shall have no outlets in that group, while outlets in the other group corresponding to the same two pairs of received digits shall occupy parts of arcs only. The Fig. 3 arrangement meets these requirements. Two additional arcs M9, M10 of the marking switch are provided connected in parallel with M3, the M9 and M10 wipers being connected to the M3 wiper over a back and a front contact respectively of PA. As shown, outlets corresponding to received digits 3 and 4 in respect of even-digit seizure of the selector occupy the whole arc, whereas those corresponding to the same received digits in the case of odd-digit seizure occupy only part of an arc. There are no outlets for received digits 5, 6 in the case of even-digit seizure ; and for odd-digit seizure these outlets occupy part only of an arc. The early part of the selector marking arc is marked for digits 3; 4 for both odd- and even-digit seizure by direct connections thereto from contacts 3 and 4 of the M3 arc ; contacts 3 and 4 in the M9 arc are connected to the later part of the selector marking arc, thus marking this part for digits 3, 4 in the case of even-digit seizure ; contacts 5 and 6 in the M3 arc are unconnected, but the corresponding M10 contacts are connected to the later part of the marking arc and mark this part of the arc for digits 5 and 6 in the case of odd-digit seizure of the selector.