Improvements in and relating to electric signalling systems, particularly wireless telegraphy and telephony

摘要

226,843. Taggart, J. Scott-, and Radio Communication Co., Ltd. June 27, 1923. Thermionic amplifiers and. detector.-Relates to dual amplification circuits in which a valve is utilized to amplify high and low frequency current simultaneously. In order to prevent any inherent tendency to instability one end of the secondary T1 of the feed-back transformer is at earth potential, the other end being connected through an inductance coil L1 to the grid of the first valve of the receiver. A pair of telephones or a loud speaker T is inserted in the anode circuit of the first valve, and is connected through a condenser C3 to the grid of the second or detector valve. In order to eliminate difficulties caused by the loud-speaker being at a high frequency potential relatively.to earth two extra coils L4, L5, Fig. 3, are wound over the tuned anode inductance L2 as shown. A crystal detector may be used, coupled through a transformer to the grid of a low frequency amplifying valve. A stabilizing resistance is preferably connected across the grid and filament of the first valve.