Abstract: A compact and lightweight emulator is provided for parasitic testing individual lighting circuits and the electric brake circuit of travel trailers and fifth-wheel trailers, which are equipped with an on-board rechargeable battery. The emulator is equipped with a flasher circuit that, when activated, flashes the stop/turn lights on the trailer simultaneously in an emergency flasher mode. The emulator includes a housing, which incorporates a 7-blade receptacle for a trailer electrical plug, a digital voltmeter, a circuit selector switch, a keyed ON-OFF switch, which selectively sends power from the trailer battery to device circuitry, and a pair of external terminals, which can be connected to leads from an electrical charger in order to recharge the trailer's on-board battery.