Transducer location differentiation in monitoring networks - uses single supply transmission line with branched distributors having resistors and diodes in series

摘要

The method is for differentiating between the various monitor locations in a distributed branched network, used typically for checking the humidity at a number of different points, or for security purposes, in which a single cable with branches, supplies all the monitoring points. Typically each monitor point (9) is supplied with current from a single transmission line pair (1) via a local diode (4) and resistance (3), the size of which is peculiar to that particular monitor location. A known current is passed down the transmission line pair (1) and the voltage across is defines the monitor point (9) being activated, or, equivalently, short circuited. A current of opposite polarity can be used to locate monitors attached directly to the transmission line pair. Two further alternative forms of the arrangement, one using a threshold defining zener diode (5) and the other diodes in both connection links between the supply line and the transducer may be used.