Telegraph distortion measuring set

Describes a testing set in which a transmitter sends out any desired signalling combination which is applied to the system under test (line and/or apparatus). The receiver is a l.v. kathode-ray oscillograph tube. The spot which appears on a fluorescent screen can be rotated by means of four deflecting plates. Each movement of the receiving relay applies a short peak impulse of several hundred volts which creates a bright spot on the screen constituting timing marks denoting the arrival of a signal. The deflecting plates are supplied with two potentials in quadrature, and a circular rotating deflecting force is thus obtained. The indication of a sequence of signals is thus a series of radial flashes whose angular positions depend upon their timing.