GB161577A - Switch arrangement for the sending and receiving of electrical oscillations, especially those of low frequency - Google Patents

Abstract

161,577. Huth Ges., Dr. E. F. April 12, 1920, [Convention date]. Void [Published under Sect. 91 of the Act]. Thermionic amplifiers.-In a, system of telephony especially for domestic use or for transmission over short distances, power lines supply plate current for a thermionic amplifier and also carry the signal currents. In an example, Fig. 1, one power line is connected to the cathode 4 of a valve and the other through a switch 7 either direct or through the primary of the receiving transformer to the anode 8. The grid 13 is connected through the switch 12 to a shunt circuit across the power wires comprising the condensers 9, 10, or through the secondary 14 of the transmitting transformer to the cathode. The condensers 9, 10 can both be variable to adjust the sensitiveness of the tube. In a further example, Fig. 3, one of the condensers in the shunt circuit is replaced by the choke coil 20 provided with a secondary winding 21, and the change-over switches are omitted. A switch 22 is provided to short circuit the receiving transformer during transmitting. Arrangements shown in dotted lines may be provided for using current from the power wires for heating the filament and supplying the microphone 16. These comprise a large inductance 23, which may be omitted, and a variable resistance 24.