Hughes Autoformer and Metal Oxide Varistor

[KYAvion]

I just purchased a used voltage booster by Hughes, and upon opening up the lid I noticed what appears to be a pair of metal oxide varistors wired between the hot leads of the female receptacle and the housing. From what I gather, the purpose of these varistors is to protect against surges. Can anyone explain to me how these varistors work, and what happens if one burns up?

[KYAvion]

No electrical gurus out there?

[silverloaf]

How about giving Hughes Tech. Support a call?
https://hughesautoformers.com/contact/