Hi,
Most Police Radar/Laser units have a setpoint they can set which will trigger an alarm if this point is exceeded by the Target. This prevents them from chasing every guy who's just a couple miles over the Limit.
Here in MN, they usually set this point at 9mph over the limit, but I've seen them have it at 12mph. This way, it doesn't disturb their Naptime...
Happy Motoring!... Jim'99