Patent GB-177218-A (GB)
Title: Improvements in or relating to arrangements for indicating the position of apparatusor the condition of circuits at a distance
IPC: G08B1/08
Filed: 1920-12-16
Abstract: 177,218. Automatic Telephone Manufacturing Co., Ltd., Electrical Improvements, Ltd., Hudd, A. E., and Beard, J. R. Dec. 16, 1920. Fire, police, and like alarm systems and apparatus.-In an arrangement for indicating, at a central or control station, the condition of any one of a plurality of remote circuits or apparatus, distinctive signalling currents indicative of the abnormal condition of the various circuits &c. are transmitted at different instants of a cyclical timeperiod, the signals being repeated at every cycle. The signalling currents may be transmitted over a line normally used for telephone conversation. As described, the arrangement is used to indicate the condition of four contact-breakers, the signals having two characteristics indicating which contact-breakers have tripped, and which one tripped first. Opening of a contact-breaker causes closure of a corresponding contact CB1 - - CB4, and energizes a corresponding magnet E1 - - E4, thus releasing a pivoted arm A1 - - A4 which thereupon rotates, together with a commutator, adapted to make contact with one of two contacts, according to the degree of rotation. The first commutator released rotates sufficiently far to make contact with the lower of two contacts connected to the negative pole of a battery B2, and also effects closure of the circuit of a motor M. Subsequentlyreleased commutators rotate only so far as to make contact with the upper of two contacts, connected to the positive pole of a battery B<1>. These results are attained by means of pointed projections 17 - - 20, carried by the arms A1 - - A4, and co-operating with balls 10 arranged in a conduit between a fixed abutment 12 and a spring-pressed member 13. The pointed member on the arm which falls first penetrates between two adjacent balls, and displaces member 13 to the right, closing contacts 22 in the circuit of motor M. The pointed member on a subsequently released arm is unable to effect further displacement of the balls, which thus limit rotation of the corresponding commutator. Each commutator is connected to a corresponding contact 31 - - 34 in a rotary distributor RD, each contact consisting of a number of members in parallel, the number being characteristic of the commutator. A contact member BA normally rests on a segment 55 so as to complete the telephone circuits, shown as comprising lines L<1>, L<2>, earthed through inductances, and bridged by the telephones T and condensers K. A polarized relay PR is inserted in line L<1> between the central station telephone and the earthed inductance, a balancing inductance BL being included in line L<2>. When motor M is started by tripping of a contact breaker and contact BA sweeps over contacts 31 - - 34, a characteristic number of negative impulses is sent to line from the commutator first released, and characteristic positive impulses from subsequently released commutators, if any. Negative impulses cause flashing of a red lamp R, and postive impulses flashing of a white lamp W. One of the Provisional Specifications describes a modified system employing three polarized relays, one operated by impulses sent over one side of a double line, another by impulses sent over the other side of the line, and the third operated only when currents of the same polarity are sent simultaneously over both sides of the line, and also describes a system in which the signalling impulses are superposed on the telephone circuits so as not to interfere with telephone conversation. This system employs transformers of known type having two substantially identical windings offering high impedance to currents through both windings in series, and negligible impedance to currents in parallel through the windings from the central point, in conjunction with signal currents of different strengths, two polarized relays responding respectively to strong and weak currents, and a relay responding to alternating currents only. In each case an indicating lamp or annunciator is provided for each contact breaker.