What is a dry contact?
Simple definition
A dry contact is a relay contact that does not supply voltage by itself.
Why it matters in wiring diagrams
It is commonly used to signal another device, such as a gate motor, alarm input or access controller.
When reading a wiring diagram, this term usually affects cable choice, power path, signal path, device selection or commissioning notes.
Common mistakes
- Assuming the term means the same thing across all brands.
- Ignoring the actual terminal names in the manufacturer manual.
- Not documenting how the term applies to the final installed system.