The DLS10 thermal delay switch very clearly shows the construction of the switch elements. The bi-metallic strip is heated by the filament (4 V) and at the correct temperature, and pre-set time (about 15 s), the switch contacts make and power can be applied to the protected device. Normally a mercury vapour rectifier.

The balloon envelope is 43 mm in diameter and, excluding the B4 base pins, is 94 mm tall.

 
Pin Connections

B4	1	2	3	4
	fc	mc	h	h

 
Absolute Maximum Operating Conditions

Delay	Vh	Ah	Va	mAa
	4.0	1.5	250	6,000

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 February 2008 {find valves by name}