What is a VDR

I have a circuit that call for a VDR acroos the contacts of a relay. I assume this is to protect against noise, or relay arcing. But what is a vdr?

bryan said:

I have a circuit that call for a VDR acroos the contacts of a relay. I assume this is to protect against noise, or relay arcing. But what is a vdr?

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VDR stands for voltage dependant resistor,
Similiar to a MOV (metal oxide varistor) that only conducts after a certain
voltage threshold is reached.
Normally having a high impedance, it rapidly drops its impedance value to absorb any spikes that may be present.

Voltage dependant resistor is term that was used a lot about 25 years ago, they used to be used in TV sets.