Patent ID: 7535346

Claim:
A trailer alarm for use with a towing vehicle having one or more vehicle indicator lights comprising: an alarm unit coupled to the towing vehicle and disposed in a first electrical circuit through which a light activation signal flows between the vehicle and a trailer, the alarm unit including: an alarm input configured to accept the light activation signal; an alarm output configured to output the light activation signal to a corresponding trailer indicator light on the trailer; and alarm circuitry configured to pass the light activation signal from the alarm input to the alarm output; detect a presence of the trailer indicator light in the first electrical circuit; and provide an alert signal when the trailer indicator light is not detected; an alert mechanism in communication with the alarm circuitry configured to receive the alert signal and provide one or more perceptible alerts in response to the alert signal; and a sensor disposed within a second electrical circuit through which a sensor detection signal flows between the alarm circuitry and the sensor and wherein the alarm circuitry is configured to detect the presence of the sensor within the second electrical circuit and provide an alert signal when the sensor is not in the circuit.