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The 37 is a low impedance low gain amplifier triode. One of its original intended applications was as an 'anode bend' signal detector. The 'anode bend' detector gives a reasonable audio gain with appreciably less audio distortion than the better-known 'grid-leak' triode detector. Use of the Type 37 as a detector became obsolete when superhets with AVC and double-diode-triode became the norm. However, the Type 37 lived on for another decade in its general-purpose role.

It would have been found in domestic receivers used for detectors, oscillators, amplifiers and AGC.

It is listed in 1951 but is removed in later information manuals.

The classic envelope is 36 mm in diameter and, excluding the UX5 base pins, is 85 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type 37 was first introduced in 1936. See also 1936 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.