Patent GB-276644-A (GB)
Title: Improvements in and relating to means for transmitting indicator readings to a distant point
IPC: G08C15/12
Filed: 1927-08-03
Abstract: 276,644. International General Electric Co., Inc., (Assignees of Allgemeine Elektricitõts Ges.). Aug. 26, 1926, [Convention date]. Tell-tale apparatus.-In a system for reproducing at a distance the deflections of measuring instruments, the receiver is operated by direct or low or high frequency current impulses, which are transmitted over line wires and are of duration proportional to the defection to be repeated, When high frequency impulses are used, they may be transmitted over power lines. In the transmitting apparatus shown in Fig. 1, the pointer 3, the deflection of which is to be repeated, operates a disc 5 having a contact 6. A fixed disc 7 is provided with a contact 8 which lies in a position corresponding to the zero position of the contact 6 and pointer 3. 'The brushes 9, 10, driven by a synchronous motor 12, cooperate with the discs 7, 5 to control a polarized relay 19 which is so connected that the armature 20 engages contact 22 to close the line circuit 24 when the brush 9 engages contact 8 and opens the contact when brush 10 co-operates with contact 6. An impulse of duration proportional to the deflection of the pointer 3 is thus transmitted over the lines 24 upon each rotation of the brushes 9, 10. The receiver, Fig. 2, comprises a disc 29 driven by a. synchronous motor 25 and clutched to the disc 35 during each impulse by an electromagnet 32 connected in the line circuit. A spring-controlled shaft 34 normally biassed against a stop 37 is thus rotated through an angle equal to the deflection of the pointer 3. The lever 35 on the shaft 34 co-operates with a spring controlled shaft 39 which carries a brake disc 44 and is adapted to set the repeater pointer 41. The pointer 41 is mounted on a spring controlled shaft 42 which carries a brake disc 46. Brake blocks 47, 48 are supported on a pivoted lever 50 which is controlled by a spring 52 and an electromagnet 51 connected in the line circuit. Normally the brake 44, 47 holds the shaft 39 in a position corresponding to the existing deflection. When the deflection of the transmitting instrument changes, the transmitted impulses energize the magnet 51 and the shaft 39 is released, the pointer remaining held by the brake 46, 48. The shaft 39 is moved back under spring control until the arm 38 engages the arm 35 which is now moved into the new position. When an impulse ceases the shaft 39 is held and the pointer 41 is released. Thus, if the new deflection is less than that previously signalled, the pointer 41 springs back until held by the extension 40. If, on the contrary, the adjustment is greater, the extension 40 moves the pointer against the action of the brake 46, 48. The relay 32 may perform the function of the relay 51 which may be omitted. Figs. 3 and 4 show a system wherein a number of transmitting instruments M<1>, M<2> operate a corresponding number of receivers A<1>, A<2> over common line wires 73. The instruments are connected to distributors 71, 81 having rotatable brushes 70, 80 which connect corresponding instruments at the transmitting and receiving stations respectively successively to the line wires. The brush 70 is driven step-by-step through gearing 66 by the synchronous motor 61. The brush 80 at the receiving station is driven through ratchet-and-pawl mechanism 79, 78 by a magnet 74 connected in the line circuit .and the arrangement is such that the brush is not stepped forward until the impulse has ceased. A transmitter Su, e.g. buzzer, is adapted to operate a signalling device Si upon each rotation of the distributor if synchronism exists. The ratchet mechanism 78, 79 may be replaced by a synchronous motor, and instead of synchronous motors, clockwork mechanism may be employed.