The servo-electric ionospheric recorder in use at the Radio Research Station, Slough, is described in relation to its general use for routine recording purposes. It contains five essential parts: (a) a pulse transmitter, (b) a pulse receiver, (c) a servo-electric control working through a discriminator to keep the receiver in tune with the transmitter, (d) a calibration unit and (e) a recording unit. This type of equipment has been in continuous use for over six years, producing hourly records of ionospheric conditions. The record consists of a graph of equivalent height of reflection of radio waves as a function of frequency. The height and frequency graticules are produced simultaneously with the echoes, and the date and time of the observations are recorded automatically.