ResonantLive Sound Archive

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

Contribute to the record

Know more about Granulated carbon transmitter?

Corrections, firsthand information, original documents, and credited photograph sources are welcome.

Your email is private and will not appear in the archive. Contributions are not published automatically.

Back to all equipment Back to Origins of electrical sound

Help build the archive

A missing piece? A correction?

Contribute to Resonant

Support the archive

Resonant is built one verified record at a time: research hours, archival image rights, and the hosting that keeps every era, equipment file, and citation free to read. If this archive is useful to you, a donation of any size keeps the next entry moving.

How donations are used
Venmo@mercer-aplinOpen Venmo, tap the pay field, type the handle, then send any amount.Send any amount · no account needed to viewCash App$MercerAplinOpen Cash App, tap the $cashtag field, type the tag, then send any amount.Send any amount · no account needed to view

Payments go directly to the archive’s editor through Venmo and Cash App. Resonant is an independent project rather than a registered charity, so donations are not tax-deductible and nothing is sold or subscribed to in return.