GB671188A - Improvements in and relating to systems of underground communication - Google Patents

Abstract

671,188. Inductive signalling. PICKERING, A. V. July 5, 1950 [July 13, 1949], No. 16765/50. Drawings to Specification. Class 40 (v). A system of underground communication comprises a high-frequency modulated carrierwave radio transmitter, a radio receiver, and an untuned and unterminated carrier wire insulated from electrical contact with the earth, or with any source of power and extending from a point adjacent the transmitter to a point adjacent the receiver, the receiver and transmitter each being provided with an aerial or the functional equivalent thereof arranged to form a loose coupling with the carrier wire. As installed in a mine, the radio receiver is situated at a convenient point undergound and the carrier wire extends along the sides of the galleries to the furthest points at which communication is required, the receiving set being mounted on a truck or locomotive, and having an aerial extending parallel to the carrier wire and spaced about a foot therefrom. Alternatively, the aerial may be in the form of a flat coil. Instead of being mounted on a vehicle the receiver may be carried by a pedestrian. The transmitting station may have a radio receiver and the movable station a transmitter, to provide twoway communication and where there are several movable stations independent communication with each is provided by using different radio frequencies. A carrier frequency of the order of 5 megacycles is used. When the transmitter receiver is installed on a battery driven electric locomotive it may be supplied by a 24-volt secondary battery connected through a rectifier to appropriate tappings on the main battery, so that should the main battery run down, power for the transmitterreceiver is provided by the 24 volt battery, and when the main battery is charged the 24-volt battery is also charged through the rectifier.