A loss prevention system comprises a protected article and a receiver. The protected article and the receiver are located in the same room. The loss prevention system can help to prevent loss or theft of the protected article. The protected article comprises a transmitter that emits an infrared signal. The infrared signal has a carrier frequency that is modulated to encode a digital signature. The receiver detects infrared signals. The receiver performs an alarm action if the receiver does not detect within a rolling time window an infrared signal having the carrier frequency that is modulated to encode the digital signature.