Condenser telephone

In the 1830's the first commercial telegraph system was constructed in England. Over time the system was perfected and across the world overhead telegraph lines were built at rapid pace to connected towns and countries. The telegraph system allowed immediate communications by Morse telegraph codes to pass important government, commercial and private messages which up until then were delivered by mail on coaches and horseback.

The Telegraph system operated for many decades until voice communications were experimented with and perfected. Voice communications over telephone equipment was trialled in the 1860's and by the 1870's basic telephone apparatus were being used in small applications. In 1877 the first successful long distance telephone line was constructed in California, USA.

Telegraph lines typically used one wire earth return circuits, this is a system whereby one conductor is installed on insulators mounted on telegraph poles. The circuit return current travels back via the earth to the origin battery. One wire on a pole was very economical to build and one wire circuits expanded rapidly to remote rural communities. Telephone circuits as distinct from telegraph circuits ideally use two wires to provide a noise free line. Once telephone communications became more commonplace in big cities there became more interest in voice telephone lines for long distance communications to smaller centers remote from the cities. Voice messages improved the correctness of the information and could allow more messages to be sent including direct person to person communications. Telegraphs typically operated between two telegraph offices and the messages written on a telegraph note and hand delivered to the recipient.

In the 1890's and 1900's the Telegraph authorities were faced with the dilemma of modernising the old telegraph systems, then in use for 40 or more years, to new voice telephone systems. The cost to convert the hundreds of kilometers of overhead 'one wire' systems to 'two wire' for telephone would have been enormous. Extra wire, crossarms, and transposition of wires to reduce crosstalk all added to the conversion cost. Where conversion could be justified by high traffic levels, meaning high income from those busy lines, they were quickly converted to two wire telephone circuits, but in many cases the cost could not be justified. A method was invented whereby a telephone circuit could be established using the one wire and earth return method similar to the telegraph circuit method.

This basic telephone circuit was known as a Condenser Telephone Circuit.