A 7 way bypass relay is connected directly to the vehicles lighting circuits to control the lights on a trailer and caravan. The relays do not put any extra load onto the vehicles lighting system. The relays also feature a built in audible buzzer that monitors the trailer and caravan indicators. All bypass relays can be powered using either the battery or the fuse box. Works on most vehicle types and most filament bulb and LED lamp combinations. Differentiates circuits on dual voltage tail/brake and tail/fog systems. Monitors indicators / flashers via the internal buzzer, which mutes under hazard warning conditions. Ancillary flasher/indicator monitor output to panel lamp or additional buzzer. Made in the UK.