A silver tungsten rod is a type of composite material typically composed of silver (Ag) and tungsten (W). It is often used in electrical and electronic applications due to its unique properties.

Barium tungsten cathodes, also known as barium-tungsten electrodes, are a type of electrode used in various electronic devices and equipment. They are indeed used in photography lamps, especially in some types of studio lighting equipment and flash units. 

Barium tungsten electrodes have unique properties that differentiate them from other types of tungsten electrodes. Here are the key differences as following: 

Barium tungsten cathodes are used in signal lights, specifically in electron tubes and cathode-ray tubes (CRTs), for several reasons: