Patent GB-192835-A (GB)
Title: Improvements in electric telegraphs
IPC: G08B9/00
Filed: 1921-11-24
Abstract: 192,835. Davis, A. L. Nov. 24, 1921. Order apparatus; lamp indicators.-A signal unit for use in a signalling system, such as is described in Specification 146,724, consists of a plunger 16 fixed to a sleeve 17 and slidable in a casing 18. A solenoid 22 surrounds the sleeve which contains a lamp 21 and carries an armature head 19 to which is hinged a cap 39 with a lens 41 and a stencil disc 42. The leads to the lamp are fixed to contact strips 23, 24 against which press blades 25, 26. The plunger is kept normally raised by a spring 20'and its movement is guided by pins 27, 28 moving in slots in the casing 18. In the raised position these pins make contact between pairs of spring contacts 31, 32 and 35. 36 and when the plunger is depressed, between other pairs 33, 34 and 37, 38. A number of these signal units 12 at a transmitting station may be connected to a similar number 12x at a receiving station, as shown in Fig. 7. One side of the solenoid and of the lamp filament of a unit 12 is connected its own terminal 38, and the other side by a wire 51 to the terminal 37x of the receiving unit 12X. The terminals 37 of the transmitting units are connected in parallel to a battery 15 through an obliterator unit 13. which when depressed breaks the connection. When any signal unit 12 is depressed, the pin 28 bridges the contacts 37 and 38 and completes a circuit through its own solenoid and through the solenoid and lamp of the corresponding receiving unit 12x. The current through the solenoid is sufficient to keep the plunger of solenoid 22 depressed, but not to depress the plunger of solenoid 22x. On the receiving operator depressing his signal unit, the pin 28x completes a circuit between contacts 37<x> and 38x and so through the lamp of the sending unit 12. A signal unit remains depressed until the circuit is broken by depression of one of the obliterator units 13 or 13<x>. The sending station may be connected to any number of receiving stations, any or all of which may be affected according to the position of the switch 49. If a plurality of receiving sets is affected, the obliterator unit in a receiving set only cancels the signals in that set, but the obliterator unit in the last set cancels also the signals in the sending set, and the obliterator unit in the sending set cancels signals in all receiving sets. The system may be arranged so that only one signal at a time may be illuminated by connecting the lead 53 from the battery to the terminals 37 through the terminals 38, 31, 32 and 34 of each of the signal units in the transmitting set, whereupon depression of any unit will cancel all previous signals by the bar 27 breaking contact between terminals 31, 32 before it makes contact between terminals 33, 34. A switch may be provided to cut out the interlocking when required. By connecting the lead 53 to the terminals 37 through the terminal 38 of one unit, the operation of all the units may be made dependent on the one. This and the former connection may be combined as in Fig. 10, in which the units 12g, 12h, 12i are dependent on unit 12f. The units 12a, 12b, 12c form one group, 12d, 12<e> a second group, and 12<g>, 12h, 12<i> a third group in which only one signal in each group may be operated at one time. The lead 53 from the battery to all the units passes through terminals 35, 36 of unit 12j so that when this latter is depressed no other signal can be actuated. The same interlocks exists between units 128 and 12f so that they cannot both be depressed at once, and neither can be operated in conjunction with any of the units 12a, 12b, and 12<c>. Morsing units 14, 14x may be provided; these are without solenoids. Other receiving units may be connected in the system shown in Fig. 10, and a selector switch provided, as in Fig. 7, for connecting some or all of them with the transmitting set.