The Philips 4152 thermal delay switch has significant switching electrodes at the top of the envelope. Such delay switches were designed to give a rectifier, such as a Mercury vapour type, time to reach working temperature before anode volts were applied. Premature application of anode Volts would lead to the early failure of the rectifier.
The wide glass tube envelope is 30 mm in diameter and, excluding the IO base pins, is 120 mm tall.
Reference: Datasheet. Type 4152 was first introduced in 1954.
Absolute Maximum Operating Conditions¶
Updated February 02, 2013.