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Mullard Radio Valve Type PM4, by Mullard, England, 1930s

Inventory Number: 21856

Number of documents: 1


Document Type: Miscellaneous Note

Document Heading: Technical Details

Text: 

The PM4 was clearly a low power device probably with less than 500 mW audio output. The 4 Volt rating usually denoted a mains device. It was produced in close co-operation with the Dutch Philips Company and hence was given the Philips-Mullard (PM) prefix. It was introduced with a series of other oxide-coated valves from September 1925; its construction was typical of most mid-1920s valve and remained unchanged for several years.


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