Visual Test Devices

A device for showing on a screen the frequency-response curve of a tuned circuit, tuned transformer, amplifier or complete radio set is described in this paper. The action of the device is practically instantaneous, and the effect of circuit adjustments may be seen immediately. The principles and operation of the device are explained, and it is shown how the derivative of the response curve may be obtained electrically and shown on the screen, to allow more accurate location of the resonant frequency, by giving a sharp crossing of the axis at that frequency. Operating characteristics and fidelity curves for the latest development of this device are given.