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The UV201A, introduced in October 1922, has a thoriated tungsten filament and replaced the UV201. The reduction in filament current is 0.75 Amp compared to the original bright emitter.

By the end of 1922 RCA held exclusive patents but valves were still being made for RCA - in this case by General Electric, who also made similar valves for Cunningham (C301A). In 1923 the UV201A was the most widely sold valve in the USA.

The valve is fully gettered and the hard vacuum valve has replaced the soft valves. The box indicates that the UV201A is intended for both detection and amplification.

This exhibit has phosphorus gettering and that was unusual. Through the bulb can be seen the vertical triode assembly.

The original box.

Thanks to Joe Gruber for sending the images.

The envelope is  mm in diameter and, excluding the UV base pins, is  mm tall.

References: ¹⁰⁴⁷ & Joe Gruber. Type UV201A was first introduced in 1922. See also 1922 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶