Abstract: A bidirectional data communications system having many remote terminals operating with a central unit includes means at each terminal for reproducing a clock from the incoming data. Upstream data from the terminals to the central unit is transmitted at the same frequency as the incoming data using the reproduced clock from the downstream transmission. At the central unit, the incoming data from each terminal is of arbitrary phase, but must be extracted without delay from the upstream transmission for data processing purposes. A clock signal substantially resynchronized with the data stream is provided by detecting the initial presence of data, and timing the frequency division of a higher frequency original clock so that the phase and frequency of the data match the clock requirements at the central unit.

Abstract: The operative status of an electrical apparatus unit such as a television receiver, incorporating an AC-DC converter, and drawing a substantial amount of current is sensed while differentiating from the usage of a lower amount of current, as when operating in a standby mode. The sensor distinguishes between the standby current waveform and a distinctly different current waveform generated when the AC-DC converter draws current in the mode in which full power is on. The sensor incorporates a reference current detector responsive to the mean of the absolute value of alternating current flowing through a power line to the electrical unit, and a peak value current detector responsive to the peak value of the periodic signal on the power line. A comparator circuit receives outputs from both detectors, and provides an output signal when the ratio therebetween is in excess of a predetermined value, this condition only applying when the AC-DC converter is operative.