Coherer, one of two

Made:
1885-1940 in Europe
designer:
Edouard Branly
Coherer, one of two

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© The Board of Trustees of the Science Museum

Coherer, one of two, designed and used by Edouard Branly, unsigned, Europe, 1885-1940 (Part of Branly collection? A182822, B3875)

Coherers designed and used by Edouard Branly, unknown maker, 1885-1940.

The coherer was the first practical device for detecting Hertzian waves. It was devised by French physicist Edouard Branly in about 1890 who did not, however, investigate its use for detecting Hertzian waves. Its most familiar form was a tube containing metal filings or turnings loosely packed between metal plugs. This presented a high resistance to current but changed to low resistance in the presence of electric waves because the filings 'cohered' or stuck together. In order to restore the high-resistance state the tube needed to be given a mechanical tap or jolt. This coherer came from a collection of apparatus associated with Branly, but it is not known if it dates from before or after 1894.

Details

Category:
Telecommunications
Collection:
Sir Henry Wellcome's Museum Collection
Object Number:
2015-541
Materials:
metal (unknown), copper (alloy), glass and paper (fibre product)
Measurements:
overall: Length = 152mm, Diameter = 11mm., Weight = 0.062Kg
type:
coherer
credit:
On loan from Wellcome Trust