Telephone condensers

A description of the production, properties and testing of condensers with wax-impregnated paper and electrodes of metal foil or metallised paper (Mansbridge type) which are used in large numbers in the telephone industry. The paper is 0.007 to 0.020 mm. in thickness with a variation of not more thanplusmn0.001 mm. The ash value does not exceed 0.5%. In foil-type condensers, tin foil 0.012 mm. thick is used, but this is being displaced by aluminium foil, commercially available in thicknesses of 0.008 mm., which has several advantages. Mansbridge condensers are "self-sealing," they are also used to make the inherent resistance condenser units. At 15deg C. a good condenser has a resistance of 5000-10,000 megohms per mF., with a decrease of 25% at 20deg C., and a power factor of frac12%.