- Item type
- Object
- Makers
- Mullard
- Provenance
- Presented by the Marconi Corporation.
- Primary inscriptions
- "REGISTERED / TRADE MARK / MULLARD / RADIO VALVES / PROTECTED BY PATENTS / 1128" printed on exterior surface of bulb. "MULLARD / PM4 / [TRADEMARK] / REGISTERED TRADE MARK" printed on exterior surface of bulb.
- Object type
- Radio valve
- Dimensions
- Diameter: 40mm Height: 100mm Weight: 0.05kg
- Inventory No
- 21856
- Accession Number
- 2004-9/338
Description
Mullard Audio Output Radio Valve (or Tube) Type PM4 with glass balloon envelope. Glass surface half-silvered and half-blackened probably during manufacturing process. The Type PM4 had a tapered-tubular bulb, with bottom seal, types, polished black bakelite base and four steel B4/M base pins.
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