Patent GB-355924-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1930-08-07
Abstract: 355,924. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, and ESCOTT, A. J., 51, Redbridge Lane, Wanstead, London. Aug. 7, 1930, No. 23674. [Class 40 (iv).] A group selector comprises two permanentlyassociated single-motion switches each having access to trunks and each adapted to mark the group of trunks to be searched over by the other. Two embodiments are described in detail. First arrangement. Fig. 1. Two 50-point switches X, Y are used, and it is assumed that there are 10 groups each comprising 8 outlets, the first four being connected to the switch Y and the last four to the switch X. Incoming impulses step the switch X, which marks the half-group to be searched by the switch 7. If the latter finds no idle outlet, it marks the remaining half-group which is then searched by the switch X. To equalize searching time, the groups, are connected in the reverse order to the switches X, Y. This arrangement is suitable for use with register-controllers, when the pause between impulse trains can be controlled. Upon seizure, relay C (1) energizes over the test wire, disconnecting battery from the a wire to initiate impulsing, while relay A energizes over the b wire, connecting up relay B, and repeats received impulses to magnet XDM and series relay C (II) to step the switch X. When relay C falls back at the end of the train, magnet YDM operates automatically to step the switch Y, and when the half group marked over wiper X2 is reached, relay R energizes over wiper 74 and completes the test circuit for relay HY, which, if an idle outlet is found, energizes and switches through. If all the outlets of the half-group are engaged, relay HY energizes in series with relay P in the next position of the switch Y and transfers the direct connections to the a, b wires over wipers Y6, Y7. Relay P marks the remaining half-group over wiper Y2 and closes a self-interrupting circuit for magnet XDM. When the marked half-group is reached, the test circuit is closed over wiper X4 for relay HX, which energizes and switches through when an idle outlet is found. If all the outlets of this half-group are engaged, relay HX energizes in the next position of the switch X and opens the a, b wires to release the register-controller, and a busy signal is sent from the first selector. The switch Y may, instead of having a normal position as shown, be of the no-normal type. Second arrangement, Fig. 2. The groups of outlets are connected alternately to two 25-point switches X, Y, each of which is adapted for simultaneously hunting over the halves of the groups appearing in different banks. As dialled impulses are received, each of the two switches acts in turn as a marker to step the other to a fresh group, and at the end of the train, the switch resting on the earlier group hunts for an idle outlet. Upon seizure, relay C (I) energizes over the test wire, and relays A, B pull up. At the first impulse, relay P (I) energizes and locks, and magnets XDM, YDM advance the switches X, Y one step; at the end of the impulse, relay Q (I) energizes in series with relay P (I), so that the switch X is in readiness for hunting over the first group if no further impulses are received. A second impulse releases relay P by closing a circuit through its opposing winding P (II), while relay Q (II) holds until the end of the impulse and then relapses. Magnet XDM operates automatically over wipers X1, Y2 and series relay C (II) to step the switch X to the third group. A third impulse operates relay P, and magnet YDM steps the switch Y in a similar manner to the fourth group, and so on. Assuming an odd number of impulses, relays P, Q remain operated, and when relay C falls back the switch X steps in search of an idle outlet under control of relays HA, HB and test wipers X5, X8 in the usual manner, the former having preference if both engage idle outlets. If all the outlets of the group are busy, relays HA, S energize in series in the next position and a busy signal is sent over the line wipers. If the number of impulses is even, the switch Y hunts in a similar way. The arrangement shown provides for 8 groups only, and if 9 or 10 impulses are received, relay HA energizes in the last position of the switch X and NU tone is sent over the line wipers. The Provisional Specification mentions a further arrangement in which one switch responds to impulses up to 5 and marks the other, which, if further impulses are received, responds thereto and marks the first switch.