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The DEQ was introduced in 1923, and was intended to replace the Q and QV. The construction is similar to the Q. The filament is a single wire running the length of the envelope and tensioned by a spring at the end opposite the anode and grid supports.

An image in the 1924 article referenced above shows the DEQ fitted to a frame with a standard B4 base.

The anode and grid connections on the envelope pass to a shaped piece of glass rod that supports the electrodes. The grid helix is clearly visible in the picture above. A distinctive feature of the DEQ is the green band of paint around the centre of the envelope.

The DEQ is a very high impedance valve and its primary function was as a detector.

The thin glass tube envelope is 17 mm in diameter and, tip to tip measures 73 mm.

References: ¹⁰⁰³ & ¹⁰⁰⁴. Type DEQ was first introduced in 1923. See also 1923 adverts.

Absolute Maximum Operating Conditions^¶