GB277740A - Improvements relating to telegraphic signal amplification - Google Patents

Abstract

277,740. Wood, K.. L., and Eastern Telegraph Co., Ltd., June 19, 1926, Addition to 246,531. Systems employing non-contact making relays.- In a system as claimed in the parent Specification movements effected by the received signals vary a capacity to disturb the balance of the system in relation to the recording instrument. In one arrangement, Fig. 1, the receiving coil 4 carries a metal plate 2 disposed between fixed metal plates 1, 3 connected to the grids of thermionic valves 5, 6 respectively. The anodes of the valves are connected through the recording instrument 10, and the anode battery 9 is connected to the junction of resistances 7, 8 of which the other ends are connected through the instrument 10. The local alternating current source 11 is connected between the plate 2 and either pole of the filament heating battery b. The system is balanced when no signals are being received, and with the source 11 disconnected, by adjustment of the filament rheostats or of one of the resistances 7, 8. The source 11 is then connected and the plates 1, 3 are adjusted in relation to the plate 2 to restore the balance. The receipt of a signal moves the plate 2 nearer to one or other of the plates 1, 3, thus disturbing the balance and causing a current to traverse the instrument 10. To enable the degree of amplification to be adjusted two additional infinitely-variable condensers may be connected in series across the source 11 with the plate 2 and the valves 6 connected across one condenser only. In a modification, Fig. 3, the plates 1 - - 3 are replaced by coils 13 - - 15, thus enabling an electro-magnetic effect to be utilized in addition to the electrostatic effect between the coils. Each coil 13 - - 15 is connected to one plate of a condenser 16 - - 18 respectively, and the other plates of the condensers are connected to the source 11 and to the valve filaments. In another arrangement, Fig. 2, the fixed plates 1, 3 are connected to opposite apices 33, 34 respectively of a bridge supplied from the alternating current source 11, and the apex f and the plate 2 are connected through the primary 35 of a transformer A provided with a series condenser 36 and a shunt condenser 37. The secondary 38, shunted by a condenser 39, is connected through a condenser 41 to the primary 40 of a transformer B, of which the secondary 42, shunted by a condenser 43, is connected with a grid biasing battery 45 in the input of a rectifying valve 44. The condensers 36, 37, 39, 41, 43 and the coupling of the transformer A are adjustable for eliminating undesired frequencies.