The term 'Master' gate operator refers to the primary gate operator which normally comes equipped with the 'Brain' of the controller, i.e. control box, board, and primary power supply. These may be used by themselves as is the case of a single swing gate operator system, where only one gate is automated. 'Slave' gate operators, or subsequent operators of the same type, are required when automating a double gate, or dual gate as they are sometimes called. Double swing gate operators automate two gates which function to cover one opening, i.e. a 20' wide double swing gate, consisting of two 10' leaves. Slave gate operators, therefore do not often require their own control board or power supply. Slave gate operators often receive their power and relay signals to open-close-stop from the primary master gate opener. A special multi-conductor, correct gauge cable is often required to carry both power and relay signals to the gate operator motor on the other side of the drive. Gate operator cables need trenched under the driveway to connect the slave (secondary) gate operator to the master (primary) gate operator. Consult gate operator manual, specifications, and user guides for correct part before ordering.