ID: 
2311
Maker's Name: 
Unknown
Dimensions: 
6.8 × 1.8 × 1.8 cm

This is used in Radar equipment. The cylindrical glass tube contains 2 convex electrodes attached to brass caps.

When the Radar set transmits, the tube discharges across the electrodes, shorting out the receiver input circuit, thus protecting the receiver from the Radar pulse energy.