Abstract: Line-seizing circuitry is disclosed by which a plurality of remote terminals may be connected to a central data recorder over a single two-wire data line with only one terminal being in communication with the recorder at any one time. Tie-breaking circuitry is included to prevent two remote units from going onto the data line simultaneously. A current source is placed across the line and when any terminal goes on the line, a resistor is also placed across the line reducing the voltage thereon below a first voltage level; the other terminals sense that low voltage and are prevented from going on the line. Each terminal includes an oscillator and may go on line only during an output pulse of the oscillator. If two terminals should attempt to go on the line simultaneously, the voltage across the line is reduced below a second and lower voltage level, and both terminals are removed from the line.

Abstract: Apparatus for controlling and recording the use of a plurality of photocopiers are disclosed. The apparatus includes a terminal associated with each of the photocopiers and a central recorder connected to each of the terminals. Each authorized user of the photocopiers is issued a badge having user identification information encoded thereon. The information on the badge is read at the terminal and transmitted to the central recorder before the copier is used while counts made at the terminal and representing the copies made are transmitted to the central recorder after the user has completed making his copies. A communication link between an individual terminal and the central recorder is only required immediately prior to and following the use of the copier by each user.