Ceramic Insulator

See full details

Object Detail

Brown glazed 'knob' or 'spool' ceramic transposition insulator with metal mount. Insulator body consists of two joined pieces of moulded ceramic. Top piece has a flat top, followed by a ridge, and then a flared skirt. Second piece has a wire ridge, followed by a wire groove, and then a small skirt. There are two sets of holes on the underneath of the insulator body, with a piece of red-insulated wire protruding from one. The body of the insulator is screwed onto a metal, hook shaped mount. The mount is threaded at both ends.
CH classification ELECTRICAL TECHNOLOGY Components insulator
Production place
L250 x W120 x H160 mm
Media/Materials description
Ceramic, metal
<On top of insulator, inside map of Australia> "E.C.C.A. \Pat No. 7926"
History and use
This ceramic insulator was used in a communication or electrical wiring system. Communication and electric line wires must be kept as dry as possible to work efficiently and to cut down on the loss of electric current. The wires are kept off the ground by being strung between poles but direct attachment of wires to wooden poles was found to give very poor results, especially during damp weather. Glass and ceramic insulators were introduced to keep the wires and the poles separated. Insulators were first used on telegraph lines. Ceramic insulators were produced in the United Kingdom from the mid-1840s. This example was manufactured in Australia.
This insulator is known as a ‘knob’ or ‘spool’ transposition insulator, used to accommodate two separate wires and to "transpose" or swap them. The wire that started on the left would end up on the right and visa versa. This was required to reduce the crosstalk that resulted when wires were run parallel to each other.

Uploaded to the Web 27 May 2011.
Registration number