Most modern radar units used by police departments display a radio frequency interference error light which notifies the operator of interference, intended or not. Radar jammers are designed to defeat police radar units and tend to be either homemade or purchased from a clandestine source in completed or kit form. While most radar jammers claim to be able to display any speed on the traffic radar that the user chooses to display. many radar jammer manufacturers are not familiar with the training of and methods used by police traffic radar operators. For example, one of the qualifications to be a certified radar operator is the ability to visually estimate speed with consistent accuracy. In general, traffic radar doctrines require police officers to spot a violator's vehicle by its excessive speed, visually estimate the violator's speed, and then confirm the estimate with radar. The commonly held belief that police officers use traffic radar as their only indicator of vehicle speed is the reason for the fascination with radar jammers. Also, the public may not realize that certain speed enforcement aids used by police officers, such as traffic laser devices, are not affected by radar jammers. 1 photograph