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'Telephone' Condenser - Marconi, Radio, circa 1908 Object Reg. No: ST 015469

Summary:
Stepped variable capacitor, made by Marconi's Wireless Telegraph Co. Ltd., London, England in about 1908. Used in radio equipment.

The 'telephone' condenser was used by the radio operator to adjust the sound of the detector to their preference or to match the tone of the transmission being received.

It is called a 'telephone' condenser because it connected in parallel across the headphone terminals (headphones were known as 'telephones' in the early days of radio).

The capacity can be adjusted in steps of 50 units from 0 to 350. The unit is a jar (1/900 µF). The wooden case contains tinfoil sheets with mica insulation, fixed in paraffin wax.
Also known as a stepped variable condenser or stepped variable capacitor.
Description:
Wooden box with ebonite top and brass fittings, two terminals and three movable pegs. One peg is broken and is kept in a bag attached to the capacitor.
Acquisition Information:
Donation from Amalgamated Wireless (Australasia) Ltd., 1924
Discipline: Technology
Dimensions: 250 mm (Height), 76 mm (Width), 126 mm (Length)

More information

Tagged with: radios, electronics, electrical condensers, capacitors
Themes this item is part of: Information & Communication Collection, Early radio: transmission and reception, 1900 - 1914
Primary Classification: COMMUNICATIONS
Secondary Classification: Radio
Tertiary Classification: components
Inscriptions: Metal plate on side of box: MARCONI'S WIRELESS / TELEGRAPH Co Ltd / No 45601 LONDON
On top on brass fittings: 50 100 200
Bottom of box: 45601
Manufacturer: Marconi?s Wireless Telegraph Co. Ltd., England, Great Britain, circa 1908
References: Wikipedia. Accessed 12 December 2012. http://en.wikipedia.org/wiki/Jar_(unit)
Bibliography:
  1. [Book], Mr Peter Jensen, In Marconi's Footsteps, 1894 - 1920, Kangaroo Press, 1994, 1994, 123 Pages
  2. [Book], Mr H. Dowsett - Institute of Electrical Engineers, Mr J. Hawkhead, Handbook of Technical Instruction for Wireless Telegraphists, The Wireless Press Ltd., 1915, 1915, 186-187 Pages

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