This datasheet tells us explanation like transmitter, speed threshold, and speed sensor. There are lots of explanation regarding speed, and acquisition are explained in the datasheet.
In this datasheet we can learn things around the speed sensor, sensor, and output. The following are grabbed from this datasheet:
Performed every 10 minutes while transmitting Stationary low speed threshold configurable: 5 MPH to 200 MPH (8 to 321 KPH) 12 MPH to 200 MPH (19 to 321 KPH) Patrol speed – Low patrol acquisition threshold configurable: Standard acquisition of 20 to 90 MPH (32 to 144 KPH), when Patrol Lo Cutoff = 20 MPH Optional acquisition of 5 to 90 MPH (8 to 144 KPH), when Patrol Lo Cutoff = 5 MPH Patrol speed, once acquired, will track to 199 MPH (320 KPH) Opposite lane target speed – 200 MPH Max closing (321 KPH) For 5 MPH (8 KPH) patrol speed: 20 MPH to 195 MPH (32 to 313 KPH) For 70 MPH (112 KPH) patrol speed: 35 MPH to 130 MPH (56 to 209 KPH) Same lane target speed – Related to patrol speed: ±70% of patrol speed within 5 MPH (8 KPH) of patrol speed i.e.
Even more, the datasheet presents discussion regarding speed range, and sensitivity.