Patent GB-366644-A (GB)
Title: Improvements relating to electric selectors
IPC: H04M19/02
Filed: 1930-12-04
Abstract: 366,644. Selectors responsive to code signals. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and HUMPHRIES, H. E., 47A, Lewisham Hill, both in London. Dec. 4, 1930, No. 36606. Addition to 334,205, [Class 40 (iv), Telephones &c.] [Class 40 (iv).] The selector described in the parent Specification is modified by using (1) a step-by-step switch to count the beats of the selfinterrupting relay device for measuring the marks, (2) a second switch or a relay chain to count the beats of another relay device to measure the spaces, and (3) a further switch or relay chain to close an alarm circuit if the signal is correct. The switches may be those known as "minor" switches in automatic telephony. A modified form of self-interrupting relay device is also described. Relay interrupter U, Y, Z. With the circuits in the condition shown (during a mark period), U(iii) is short-circuited to make it sluggish Y(i) energizes to complete a circuit for U(i) and also prepare a circuit for Z(i) over Y(i) which becomes operative when U pulls up. Z opens the circuit of U which falls back slowly. The windings of Y are now operating differentially so that Y falls back and U(ii) pulls up slowly. Z, which has held over Z(ii), releases and U again falls back slowly. The circuits are again in the condition shown and the cycle is repeated. The relay characteristics are adjusted so that the duration of a cycle is just less than half a second. Relay U is alternately energized over (i) and (ii) wound in opposite direction to prevent remanent magnetism. At the end of the period to be measured the short-circuit about U(iii) is removed and the combination quickly restores to normal. First mark; measurement by switch A. This mark is of 4 seconds' duration but the selector tolerates a mark lying between 3¢ and 5¢ seconds. On receipt of the mark, relay S in the output circuit of a wireless receiver falls back and short-circuits normally energized relay SA to start the interrupter U, Y, Z. The stepping magnet AM of switch A operates on each energization of Y. If the mark endures for 3¢ seconds, magnet BM of the recording switch B operates over A1 and seventh contact and the switch takes a step, but if it endures for 5¢ seconds the switch B is released by magnet BR operated over eleventh contacts. When the mark ceases, release magnet AR restores switch A. First space. The spaces are of not less than one-fifth of a second and not longer than 1¢ seconds' duration. Magnet CM of the space switch C received an impulse over A3 during the seventh cycle, so that when SA operates on cessation of the mark, X(i) pulls up and C takes another step. X(ii) energizes and opposes the flux due to (X)i, which is now open-circuited, whereby a release and reoperation of X occurs and C takes a further step. The stepping continues for the maximum allowable period of the space, independent of the condition of relay SA, until W(i) pulls up, completes a series circuit for W(ii), and release magnet CM so that switch C restores and W falls back. If the space has not terminated, switch B is released over BR, C3, B2, sa1 (operated). Subsequent marks ; completion of alarm circuit. The second and third marks are timed like the first and if correct L operates over B1 which has taken three steps and A2 which has restored to normal. Relay L opens the shortcircuit about SA so that further signals are ineffective, and closes the circuit of alarm AB. If the second mark is too short, switch C will not take its initial step so that when the mark ceases, switch B will be released over the circuit described in the last sentence of the preceding paragraph. Re-setting. After receipt of a correct signal, switches A and C are normal and B in the position described in the preceding paragraph. Closure of re-set key RK operates release magnet BR to restore B which releases L. Faults. If a valve filament fails, a relay may be released to complete a connection over x for the alarm AB.