Gas Tube or Spark Gap arrestors

This technology is still used to protect insulation in cabling including some telephony applications.

Its best feature is of a near zero current conduction, until the gas between the electrodes ionises. Once conduction begins only a return of the current back to zero, allows the arrestor to switch off.

For this reason, this device is also known as the crowbar suppressor. Normally a fuse is needed upstream so as to cut the current off. Unfortunately the equipment being powered must experience a power outage when the protection activates.

Note: This is not a suitable device for protecting electronics