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Equipment file · Telephone transmitter

Granulated carbon transmitter

Henry Hunnings · 1878–1881

Evidence status · documented

Identity and core specifications are documented; some historical fields remain unavailable.

Henry Hunnings, a curate near York, developed a transmitter using loose carbon granules between two platinum electrodes behind the diaphragm, patented in Britain in 1878 and the US in 1881. On 27 January 1880 it was demonstrated over about 45 miles of telegraph wire between Darlington and York. Hunnings sold the patent to Edison, but the granule principle became the long-term standard.

Introduced
1878–1881
Category
Telephone transmitter
Intended use
Carbon-granule transmitter for louder, longer-distance telephony
Production
Made from 1880 in Darlington as the 'Hunnings Micro-Telephone'; descendants in GPO use into the 1980s

Equipment photographs · 1

US patent 246,512 (1881): granulated-carbon transmitter

1 / 1 · US patent 246,512 (1881): granulated-carbon transmitter

US patent 246,512 (1881): granulated-carbon transmitter·Henry Hunnings·Public domain (US patent)

Why it mattered

  1. 01

    Granulated carbon gave a stronger, clearer signal than button designs, and became the basis of nearly all later carbon microphones, including those used with early PA amplifiers.

  2. 02

    Refined versions resisted granule packing and stayed in British service for a century.

Engineering record

Operating principle
Loose carbon granules between two platinum electrodes; diaphragm pressure lowered their resistance[1]
Known failure mode
Granules settled and packed, reducing sensitivity; Deckert's ridged electrode kept them spread[1]

Original pricing

No reliable period price located

2026 equivalent

Not calculated without a reliable original price.

Public price evidence was not sufficient to publish a defensible original figure.

Use in the field

Demonstrated 27 January 1880 over about 45 miles of telegraph wire between Darlington and York[2]

Manuals & original documents

No authoritative manual or original document has been located for this profile.

Sources

  1. 1Carbon Telephone Transmitters - 4: The Hunnings and Deckert Transmitterssamhallas.co.uk · reference
  2. 2Rev Henry Hunnings MA (1842-1886) – Clergyman & InventorAll Saints' Church, Bolton Percy · archive
  3. 3Henry HunningsYorkshire Philosophical Society · archive

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