# What is this component and what is its use?

I found this in CRT TV on the CRT tube driver PCB.

What are they and what is their schematic symbol?

• An overvoltage spark gap perhaps? May 23 '14 at 10:02
• Was is directly connected to the pins on the CRT? If yes its almost certainly a spark gap. May 23 '14 at 10:04
• What is that cloudy-white plastic material around it? Is it rubbery, flimsy, solid, etc.. Jul 31 '14 at 18:22
• @Funkyguy it is solid, not at all rubbery. Jul 31 '14 at 18:23
• IS there an actual gap between the wires in side the part labelled with "air gap" from the pictures it looks like a nick in the wires but there could be a small gap in there too. Jul 31 '14 at 18:43

As noted in comments, the part shown in the photograph is a spark gap. This page lists several such spark gaps and similar / related parts.

Below is an inert-gas filled spark gap, closest in functionality to the part in the question, yet safer due to being glass encapsulated:

A more common modern version of this device is offered by Littelfuse and others, and comes in several different packages:

The through-hole versions are available on eBay for around $1 to$2 in single units, if you would like to experiment with one.

Various schematic symbols for spark gaps are documented on WikiMedia:

Of these, symbol #2 is most commonly supported in the schematic software I have used.

• To me, #1 is a surge arrester (i.e. metal oxide varistor.) #4 is a generic symbol for variable resistance, i.e. a temperature measuring thermistor. I would use #2 for a spark gap. Aug 1 '14 at 4:26
• For info, the Littelfuse style gas-filled spark-gaps are used extensively in telecomms for lightning protection. In fact, give or take every UK phone line has one across the end where it enters the telephone exchange. Aug 1 '14 at 9:18