LG71 TR cell

This device measures 77x29mm overall.

The LG71 is a TR switch with a diameter suitable for insertion into a 70 ohm concentric line. The first of these was made with soft glass but due to the high sodium and potassium content the glass tended to absorb the water vapour filling. Later ones were made from a hard glass with a low alkali content. However the hard glass led to problems with delay time and so thorium was introduced.

The metal part of the device is in air. A tube runs through the glass envelope and is open at each end, and the metal part is held in this.