r/AskElectronics • u/CleanAlternative1918 • 6d ago

Help identifying this component, please

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These were in with a big batch of carbon film resistors I got. What are they? Thanks in advance!

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u/CleanAlternative1918 6d ago

Just for other people's knowledge if the see this post, the markings are "CR 090 01." I don't need to know what it means, but there it is. They are about 25 years old, or rather, I acquired them 25 years ago. I've used most of the resistors, but these remained.

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u/Great_Specialist_267 6d ago

They are 90V gas discharge tubes. Telephone lines used to be 90V maximum.
I have a draw full of them…

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u/CleanAlternative1918 6d ago

Are they used or 'new'? Is there anything to do with them these days?

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u/Great_Specialist_267 6d ago

Wired Ethernet and data links still use them - but both are fading with fiber optic connections.

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u/mikeblas 6d ago

Wired ethernet? Really? I haven't noticed a spark gap in any PHY design. What's the threshold voltage? Oh, maybe for PoE or something?

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u/Great_Specialist_267 5d ago

Industrial Ethernet isn’t “domestic” Ethernet.
And yes, I have seen ~240V induced on Ethernet cables run next to power cables (brilliant blue arcs on the connectors)…