GB1031994A - Improvements in inductive signalling systems for mines, tunnels and similar situations - Google Patents

Abstract

1,031,994. Inductive signalling. JOHN DAVIS & SON (DERBY) Ltd. Jan. 22, 1965, No. 2820/65. Headings H4L and H4U. In an inductive or radio signalling system for mines or the like a portable receiver is associated with the lamp circuit of a miner's lamp so that the lamp is dimmed or extinguished in response to signals from the remote transmitter. In one arrangement a radio transmitter is situated at a motor control point and provided with an aerial which extends throughout the whole working area and consists of an insulated cable in which the conductor forms a loop within the cable. When the motor switch is operated a signal is sent via the transmitter and aerial to the remote receivers which may be associated with cap or hand lamps and tell-tale lamps situated at convenient positions. Audible warnings also may be operated. The aerial loop may include a warning device comprising a high impedance or a rectifier at its remote end, a high resistance and a low resistance relay being connected in series in the loop and a suitable current being passed through the loop to energize the high resistance relay, this condition being maintained so long as the aerial is intact. A shortcircuit on the cable will cause a higher current flow to operate the low resistance relay. The receiver may be built into a lead connecting the battery to a cap lamp or may be built into the lid of the battery box. An alternative arrangement uses an inductive loop enclosing the working area.