An intercom gate entry system is used at security gates so visitors can press a button when they arrive and contact someone inside the gated area. These intercoms can be wireless or wired depending on the environment they are used in.
Wireless gate intercoms are available in models that use 2-way radio frequencies, digital, cell phone based, and Wi-Fi. Factors to consider when choosing a wireless intercom are the distance between the gate and building, building constructions, obstructions in the way, and whether or not you want to take calls from the gate even when you aren't on the gated and fenced property.
Wired intercoms require running wire between the gate and an inside intercom station. There are distance limitations on these devices as well so the distance between the two is important to know. This includes the length of the wire inside the building as well.
All these systems allow for remote gate opening if you have an electric gate opener installed. You just need to run two wires between the intercom and the gate controller circuit board. The gate opening is activated by a button press on a telephone keypad, an inside intercom, or a handheld radio.
You can find more info on gate intercom entry systems by clicking here.