Spec Sheet Preview: The Alpha Communications® 7111 and 7113 door contact switch units are typically installed (mortised) into a door frame to allow electrical current to flow thru to an electric door strike (or equivalent unit), without the need for exposed door loops. The model 7111 features 2 heavy duty plated spring contacts and the 7113 features 3 heavy plated duty spring contacts to assure positive electrical connections. Both models are designed for low-voltage operation.