GB191777A - Improvements in and relating to signalling systems - Google Patents

Abstract

191,777. Taggart, J. Scott-, and Radio Communication Co., Ltd. Sept. 12, 1921. Thermionic detectors; atmospherics and undesired signals, eliminating or limiting. - Relates to current limiting devices, particularly for lessening interference in wireless reception. The high - frequency currents are preferably rectified and applied as uni-directional currents to a twoelectrode valve, to the grid of a threeelectrode valve, or to the negatron " described in Specification 166,260. As shown in Fig. 1, the received waves are amplified by valve Vo and rectified by a two-electrode valve, V1 the circuit of which includes a condenser C, and resistance R connected across the grid and filament of the " negatron " V2. By this arrangement, all rectified impulses are reduced to the same wave form before being applied to the limiter. The " negatron " is adjusted to work at the point X, Fig. 2, so that a strong positive impulse carries the applied voltage over the peak of the curve and may produce less effect than a weak impulse. The " negatron " may be replaced by a three-electrode or a two-electrode valve working at the lower or upper bend of its curve, a small positive potential being preferably applied to the anode of the two-electrode valve. In a further arrangement, using two valves V1, V2, Fig. 6, connected reversely to the input terminals X, Y, the valve V1 is adjusted to operate near the bottom of its curve, while the grid of the valve V2 is made so negative that no current passes until the incoming positive potentials exceed the potential of battery B2. Normal signals influence the valve V1 only, but strong signals or atmospherics cause the current in valve V1 to become zero and an increasing current to flow through valve V2. Specifications 158,762 and 185,133 also are referred to.