Patent GB-244486-A (GB)
Title: Improvements in or relating to wireless and like signalling installations
IPC: G01S11/02
Filed: 1925-12-11
Abstract: 244,486. Goldberg & S÷hne Ges., M. J. Dec. 11, 1924, [Convention date]. Fire and like alarm systems.-In a signalling system employing high frequency oscillations the absorption at one or more local stations of energy transmitted by a central station is arranged to give an indication when the frequency of an oscillating system varies at a rate greater than a predetermined value. The local apparatus may comprise an oscillating circuit, the natural frequency of which is varied by a moving body such as a burglar varying the inductance or capacity of an aerial or by heat causing a similar variation. Fig. 11 shows a system of three local stations 300, 301, 302 coupled to a central station by a single wire adapted to operate alarm bells 349, 352, when the natural frequency of the aerial systems is varied at a rate greater than a predetermined value. The oscillating valve 294 is successively tuned to the frequency of the three aerials at the local stations by condensers 312, 313, 314 switched in parallel with the inductances 296, 297 by the distributor 307. Condensers 329, 330, 331 are arranged in parallel and adjusted by heating coils 324, 325, 326 controlled through amplifying valves 333 and relays 334, 342 to maintain resonance between the tuned circuits and the local station aerials for variations due to slowly operating natural changes. Departures from resonance at a more rapid rate cause relay 334 to close contact 339 thus causing relay 342 to close contact 328 and actuate the bells of which 349 is actuated till the regulating system has restored resonance, and the bell 352 until the flap 350 of relay 348 is hand restored. An additional set of contact segments may be provided on the distributor 307 to actuate drop indicator discs to show which local station is affected. 'Various forms of regulating devices are described in which heating coils vary capacity or inductance and also relay controlled mechanical devices for the same purpose. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a fire alarm system in which a wire connection may be made or broken by heat melting an insulator or a fusible conductor or an inductance or capacity may be varied by the expansion of a liquid or gas or by the expansion of a composite metal strip. In a burglar alarm system the object to be protected such as a safe, fence or telegraph line may be used as antenna. When a line is protected it may be divided into sections 6, Fig. 2 (Cancelled), separated by chokes 5, each section being provided with a local apparatus 7. When an aerial 21 is employed it is protected from local disturbances including that caused by varying earth conductivity by screening it from the interfering source. In addition springs may be employed to prevent the operation of the alarm by sagging and balanced aerials may be employed to prevent variations such as rain which affects both from operating the alarm. The sensitivity of an aerial or a part thereof may be varied by the insertion of condensers 40, 45, 46 or inductance 43, Fig. 10 (Cancelled). Similar arrangements or a variation of the oscillatory frequency used may be employed to transfer the important positions at the local stations away from nodal points. The oscillation generator 48, Fig. 12 (Cancelled), may be provided with various resistances, capacities, inductances and coupling and potentiometer controls to maintain a constant oscillation frequency. Similar means may be employed to increase the resonance. The local station 78, Fig. 18 (Cancelled), may be connected to the central station 84 by wires 75, 76, 77, or if an alternating supply is used for the valves one of the wires may be dispensed with. Alternatively, the connection between the local and central stations may be an earth signalling system or wireless, Fig. 21 (Cancelled), in which aerials 102, 103 are influenced and the aerial 104 is used for the transmission of signals. The receiving aerial 105 is connected through an amplifying system to an indicator connected to the leads 108. The aerial at the local station which is influenced to operate the alarm may also be employed for the transmission of signals. In a fire-alarm system in addition to the aerial being broken or two aerials being connected together by the melting of a solid body the expansion of a solid, liquid or gas may be utilized to make or break electric connections or to vary the capacity of a condenser and means may also be provided to vary the sensitivity of such apparatus. This subject-matter does not appear in the Specification as accepted.