Remote indication by a Wheatstone bridge system

The Wheatstone bridge method of resistance measurement is noted for its simplicity, accuracy and reliability. It is claimed that these attributes can be retained in remote-indication systems which employ the principle of the balanced bridge. This method ensures freedom from any undesirable effects of self-inductance, capacitance, induced voltage or supply-voltage variation within normal limits. A detailed description is given of an automatic signalling system of this type which has been in continuous operation since 1929 in Georgetown, British Guiana, under extremely onerous conditions. The paper also indicates how the balanced-bridge principle may be developed to superimpose telemetering facilities on a single-pair telephone circuit. Two appendices set out general formulae and examples of their application in the design of the Georgetown installation.