This current conduction switch automatically switches a second device on or off when a DC device is switched on. For example, the radio automatically switches off when the CB radio in the car is turned on, or the radio amplifier automatically switches on when the CB radio transmits. It can automatically switch off an outdoor caravan light when the interior light is switched on. It can also be used to check whether vehicle lights are working (current conduction test). The module is simply connected in-line with the power supply of the device (6–30 V/DC) & uses a potential-free contact (1 x UM, Max 3 A) to switch other devices on & off. The module responds to currents between~ 1–5 A.