The horn relay supplies battery positive voltage (B+) to the horns when energized. Battery positive voltage (B+) is supplied at all times to the battery positive voltage circuit of the horn relay coil and battery positive voltage circuit of the horn relay switch. Pressing the horn switch grounds the horn relay control circuit. The horn relay control circuit can also be grounded by the dash integration module (DIM). The DIM receives a message via class 2 from the RFA module to sound the horns. The DIM then energizes the horn relay by grounding the control circuit. The horns sound until the horn switch is released or the DIM de-energizes the horn relay.