An exit loop is wire that is either buried beneath the driveway or cut into the concrete or asphalt. It is located behind the gate. Locating it far from the gate is best. A vehicle triggers the loop, which acts like a big metal detector and opens the gate, allowing the vehicle to exit.
Loops are a weak spot in many gate systems. All loop connections must be soldered and any underground connections completely waterproofed in order to avoid problems. The size, shape, and number of turns of wire in the loop will determine the sensitivity. Loops cut into asphalt or concrete should be 1" or more deep. Those buried in earth or gravel should be 4-6 inches.
Safety Loops, Miller Switches, and Photo Eyes"Safety" loops are buried or cut in the pavement in front and behind a gate. They prevent the gate from closing on a vehicle in its path should it stay there past the "momentary open" timer setting.
"Miller edge" switches, long strip switches as found on elevator doors, are required on slide gates at each end to prevent entrapment.
Photoelectric "eye" and safety loops are often used in combination with one another.
A single photo eye may be used on a slide gate to hold the gate open in case a vehicle stays too long in its path or reverse if a vehicle enters its path as it is closing. Other "entrapment zones" created by the gate, i.e., sliding behind a fence or wall, require a photo eye as well. |