| | |   HP-45B hydrogen thyratron. A thyratron is a vacuum tube used to switch on high voltages.  They act like a switch that can be turned on by applying a small voltage to a control terminal.  They can only switch on, not off: They turn back off only when the voltage being controlled drops to zero on its own.  The modern equivalent is the SCR (silicon controlled rectifier) and triac.
 This one contains a small (less than atmospheric pressure) amount of hydrogen gas instead of a pure vacuum.  Various different gases are used in thyratrons, and apparently the hydrogen variety is used when particularly fast switching times are required.
 Source: eBay seller tapent
 Contributor: Theodore Gray
 Acquired: 24 February, 2007
 Text Updated: 29 April, 2007
 Price: $5
 Size: 5"
 Purity: <1%
 | 
 |   | 
 |