The HORN mini fuse in the underhood fuse-relay center applies the voltage at all times to the horn relay. Depressing the horn switch closes the horn switch contacts. Closing the horn switch contacts provides a ground to the coil of the horn relay. Grounding the coil of the relay energizes the relay. Energizing the relay and closing the contacts applies the battery voltage directly to the right side horn and the left side horn. Since the right side horn and the left side horn ground at ground G101, the horn will sound as long as you press the horn switch.