Patent GB-184784-A (GB)
Title: Improvements in apparatus selectively responsive to electrical call signals
IPC: H04L15/26
Filed: 1922-07-06
Abstract: 184,784. Soc. Franþaise Radio-Electrique. Aug. 19, 1921. Electric selectors.-An arrangement whereby a bell &c., mav be operated in response to selective call signals, applicable to wired or wireless systems, and as a selector for telemechanical control, or as a telgraphic or telephone selector, ccmprises a member adapted to be moved stepby-step on the receipt of a predetermined series of electric impulses to actuate the bell &c. when moved the predetermined number of steps, but returned to normal if any of the impulses received do not conform to the predetermined series, or if the received impulses are preceded or followed by an impulse not proper to the series, or if the intervals between the impulses are not of correct length. A key 1, operated manually or by a relay responsive to received impulses, energizes, 'when closed, a magnet 2, the armature of which effects step-by-step movement (one step for each energization) of a member 5 by means of a pawl 4 and also controls two sets of reversing contacts 6, 7. When magnet 2 is energized, contacts 6 close the circuit of a magnet 8, which closes its own hold-on contact 9, and, by contact 10, breaks the circuit of a slow-acting relay 11. This results in the opening of contact 26 in circuit with magnet 8, and in contact 12 being closed after an interval corresponding, say, with a dot impulse, connecting the negative pole of a current source with one or other of two wires 14, 15 according to the position of contacts 7 as determined by the energized or de-energized condition of magnet 2 when contact 12 closes, depending upon whether the impulse received was a dash or dot. The member 5 has a projection 16 which successively earths contacts 17, 18, 19, 20, these contacts being connected to wires 14 or 15 according to the predetermined impulses to which the device is to respond. Earthing a contact which is at the time connected to battery through wire 14 or 15 and contact 12, energizes a release magnet 23 and returns the member 5 to its original position. If the correct impulses are received, projection 16 successively passes contacts 17, 18, 19 and engages contact 20, at the same time closing contact 22. A retarded magnet 27, energized by contact 10 each time magnet 8 is energized, controls the predetermined permissible interval between the received impulses. If the interval between received impulses exceeds a predetermined value, contact 28. controlled by magnet 27, energizes release magnet 23, if projection 16 rests on a contact 17, 18 or 19, but if the long pause follows completion of a correct signal, projection 16 being at contact 20, a magnet 31. controlling the local circuit of the alarm bell S is closed. Magnet 31 closes its hold-on contact 34 and the bell continues to ring until the hand-operated switch 35 is opened. The contact 33 which closes the circuit of the bell S breaks the circuit of magnet 2 and prevents interference by the subsequent receipt of signals. Should the received signal contain an additional impulse following a correct sequence of impulses, member 16 is stepped round to a contact 21 before magnet 27 effects closure of the bell circuit, and release magnet 23 is energized. The number and connections of contacts 16, 20 are dependent upon the selected signal to which the device is to respond, and response of the device may be arranged to depend upon a repetition of the correct signal. To minimize the number of contacts, the bell-circuit may be provided with a number of breaks which must be successively closed by the receipt of predetermined signals.