Wet vs. Dry Contacts: Knowing the Difference - Technical Articles
relay - What is a "dry contact input"? - Electrical Engineering Stack Exchange
dry contact control relay - Am I on the right path - Electrical Engineering Stack Exchange
Dry Contact Closure Wiring Diagram For A DWA-S Sonachron Program Timer – Lathem Time
Understanding Dry Contact Terminology and How It Applies with Respect to the Bi-Directional Amplifier (BDA), Battery Backup Unit (BBU) and Fire Alarm Control Panel (FACP) Equipment