GB503420A - Improvements in or relating to electrical oscillator apparatus for medical purposes - Google Patents

Abstract

503,420. Valve generating and modulating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and LAY, A. W. Oct. 5, 1937, No. 26970. [Class 40 (v)] [Also in Group VI] Electro therapeutic apparatus comprises a relaxation oscillator circuit, an oscillator circuit including a valve having at least a grid and an output electrode and so arranged that normally self oscillation does not occur, means for applying impulses from the relaxation oscillator circuit directly to the grid of the valve so that oscillation occurs when an impulse is applied and then dies away, and an output circuit fed from the output of the valve oscillator. In the arrangement shown, the impulses from the relaxation oscillator circuit, comprising neon tube V3, resistances R2 and P2, and condenser C7 (or a number of condensers in parallel) connected across a source of D.C. potential, are applied to the grid of valve V2 through a coupling circuit C8, P1. This valve may be an indirectly heated tetrode, having a Hartley oscillatory circuit, C9, L1 connected between the screen grid and anode, and negatively biassed by resistance R1. Transformer L2, L4 feeds the output circuit. The frequency of the relaxation oscillator is controlled by resistance P2 and may be of the order of 10 to 500 impulses per minute, and their amplitude may be controlled by potentiometer P1. The resistance P3 controls the oscillatory condition of the valve V2. In an alternative arrangement, the Hartley oscillator circuit is connected between the control grid and screen grid of valve V2 and the positive impulses are fed from the potentiometer P1 through a series resistance.