Patent GB-342707-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: G01R17/08
Filed: 1929-08-02
Abstract: 342,707. Synchronism indicators. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Aug. 2, 1929, No. 23821. Convention date, March 18. Addition to 316,228, [Class 40 (i), Electric signalling systems &c.]. [Class 37.] Relates to a system for repeating at a distance variable values, such as the indications of a measuring instrument in a manner similar to that described in the parent Specification wherein the primary torque of the instrument is balanced by an adjustable electrical force the value of which is transmitted for distant indication. Instead of balancing the torque, however, a resistance included in a Wheatstone bridge is periodically adjusted according to the indication of the instrument and balancing is automatically effected by appropriate combinations of fixed resistances. Transmitting apparatus. As shown in Fig. 1, resistances 3, associated with the instruments 1, are successively associated by a distributor 80, with resistances 4, 5, 6 .. 10 which form the other arm of a Wheatstone bridge arrangement controlling a polarized relay 12. The pointer 1 of the instrument is periodically depressed by a pivoted frame 2 to insert in the bridge a resistance 3 proportional to the instrument reading. If the bridge is thereby unbalanced relay 12 is operated to close contact 14 and prepare locking circuits for relays 62 .. 102 which control the short-circuiting contacts 61 .. 101 of the resistances 6 .. 10. A rotary switch 23 which is released when the frame 2 is operated, operates the relays 62 .. 102 in turn over contacts 27 .. 35 the relays corresponding to the resistances required to be short-circuited to effect balance locking up over contacts 28 .. 36 and projection 26 when relay 12 moves into engagement with contact 14. The relays not required to effect balance, although temporarily energized are not maintained by reason of the opening of contacts 13, 14. The relays 62 .. 102 control further contacts 64 .. 104 which are connected to the contacts 52 .. 56 of a distributor 50 which during the second halfrevolution of the shaft 40 transmits impulses to the receiving station when the arm 51 engages contacts marked by the locked relays. The system may be adapted to transmit indications of the product, quotient, sum, difference or ratio of several quantities or the square or square root of a quantity. Receiving apparatus. At the receiving station a distributor operating synchronously with the distributor 50 effects the energization of receiving devices corresponding to the locked relays at the transmitter. A receiving device of the type shown in Fig. 5 of the parent Specification may be used to ensure accurate transmission. Synchronizing. In a method of indicating the synchronism of two alternating current sources (Fig. 2 not shown) relays adapted to control corresponding resistances of different values are connected between similar phases of the two sources. When the frequencies of the two sources differ the relays are energized in cyclic order to connect the corresponding resistances into a Wheatstone bridge circuit in turn. Balancing is effected by resistances and switching apparatus in a manner similar to that described with reference to Fig. 1, and impulses are transmitted to operate a synchronoscope of the rotating field or lamp type. A single Wheatstone bridge arrangement may be selectively associated with a plurality of generators and measuring instruments. The Specification as open to inspection under Sect. 91 (3) (a) states that in the system for indicating synchronism the Wheatstone bridge connection may be dispensed with, impulse transmission being effected directly by the phase relays. This subject-matter does not appear in the Specification as accepted.