Abstract: A communications system is disclosed including a radio junction box controlling a number of radios and a number of crew boxes all linked by a ring circuit consisting of a single coaxial cable which provides both power supply and information. The various communication channels between the crew boxes and the radios and an intercom channel linking the crew boxes are provided by time division multiplexing. The microphone of each crew box is coupled to the coaxial line by a current generator. Each current therefore generates an appropriate voltage signal across the impedance of the cable which is assumed to be constant. Thus, when more than one crew box feeds current onto the line, the currents add and generate a correspondingly greater voltage signal on the line.

Abstract: The system described is for controlling the "rapid" charging of electric batteries whose voltage-time profile exhibits a peak at or about the point when it is fully charged, and is arranged to curtail the charging when this peak is detected. The system may be time-multiplexed to control the charging of a plurality of batteries simultaneously. The peak may be detected by comparing each successive sample of the battery voltage with the preceding sample. The system may include means for adding to each sampled voltage, before it is compared with a previously stored sampled voltage, a predetermined reference increment, whereby to avoid errors due to jitter of the sampled voltage. In such a case, means are preferably also provided for inhibiting up-dating of the stored sampled voltage when the comparing means detects that the next following sampled voltage increased by the said increment has fallen to the same value as the stored sampled voltage.