INTRODUCTION Logarithmic Amplifier TM 9954 is intended for use in swept frequency applications to expand the dynamic display range of detected signals and to present this range on a logarithmic scale. Hence each equal factor of change in r.f. input level produces an equal increment of change in output voltage, enablingthe oscilloscope display tobe calibrated linearly indB, e.g. lQdB/cm. As well as the logarithmic mode described above there is also a DIRECT mode in which the input from the detector is connected directly to the output. The DIRECT mode is used for calibration and also eliminates the need to disconnect the instrument when the logarithmic function is not required. The instrument is self-powered by mercury cells and battery life will typically be in excess of two years.