Battery voltage is applied to the horn relay at all times through the horn circuit breaker. When the horn switch is pressed, the horn relay coil is grounded. This action energizes the horn relay, the relay contacts close and voltage is supplied to the horns. Since the horns are permanently grounded at G102 (L21/LP4) or G101 (LG5), the horns will continue to sound as long as the horn switch is pressed.