When using an external relay module such as the IP Quad Relay (WEBRELAIS), the most secure setup is to install the module inside on the secure side of the door. Many installers do this inside a secured technical room or cabinet. 

This makes the switching for door or gate actions occur inside the building, meaning it's more secure and less vulnerable to tampering. 

In some environments, such as corporate, industrial, or high security locations, policies or regulations may require that relays are not installed outside the building. Using an internal relay setup helps installers to meet these requirements and improves overall system security.