GB480424A - Improvements in or relating to electrical phase and polarity reversing networks - Google Patents

Abstract

480,424. Valve circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 9, 1937, No. 21906. Convention date, March 10. [Class 40 (v)] A four-terminal phase or polarity reversing network comprises a potential divider of two resistive, or reactive impedances of the same phase angle and nearly equal values, R1, R2, Fig 4, connected between input and output terminals 1, 3, the point ug which is preferably adjustable being connected to the grid of the amplifier valve V whose anode is coupled to output terminal 3 The cathode of the valve is connected to input and output terminals 2 and 4 which are common, and if instead of the blocking condenser C, a source of voltage to oppose the anode supply BA is employed to couple the anode to terminal 3, the network is capable of reversing D.C. polarities. The push-pull voltages obtained between terminals 3, 5 may be used to feed a push-pull amplifier stage or feed a balanced two-wire line from a concentric cable, particularly at television frequencies where transformers are unsatisfactory. The grid-anode capacity of the valve V may be compensated for by connecting an equal capacity across the element R1. In an embodiment, Fig. 7 (not shown), the amplifier valve V and the valve supplying the input terminals are combined as one double triode valve. Fig. 8 shows the device employed to obtain sum and difference voltages for application to a push-pull modulator. The modulation Vo is applied between terminal 2 and a datum 8 such as earth, the carrier u being applied between terminals 1 and 2. Voltages Vo + u, Vo - u are obtained between terminals 5 and 3 and the datum 9, and applied to the modulation circuit consisting of resistances W1, W2 and rectifiers G1, G2.