THE PERFECT PATROL SPEED WITH VSS
Traffic Radar Patrol Speed Measurement
Moving traffic radar systems normally obtain patrol speed by measuring the speed of the radar return from the moving roadway in
front of the moving vehicle. Patrol speed tracking sometimes suffers from anomalies known as “batching” and “shadowing.” These
anomalies occur during moments when the roadway is obstructed from the radar beam by road conditions or other vehicles. The
solution is to allow the traffic radar to monitor vehicle tire rotation and to use this information to perform “patrol speed steering.”
There are two ways to monitor tire rotation. One way is through the CAN Bus using Stalker’s exclusive CAN/VSS Adapter; the other
is to attach directly to the Vehicle Speed Sensor (VSS) signal in the patrol vehicle.
The CAN/VSS Solution – VSS Advantages without VSS installation problems.
You can skip VSS installation when you use Stalker’s CAN/VSS Adapter to power your Stalker radar in the patrol vehicle. Unlike
connecting to the vehicle’s VSS, which can be a challenge to locate, the OBDII diagnostic connector is easy to find and takes only
seconds to connect.
Locate your vehicle’s OBDII connector. Connect the Stalker CAN/VSS cable.
The CAN/VSS Adapter is Stalker’s preferred method for automating the radar’s patrol speed acquisition as well as transitioning back
and forth between stationary to moving modes.
The VSS Speedometer Signal
All modern vehicles have a VSS sensor (Vehicle Speed Sensor) attached to the transmission or an axle that generates a speed signal.
The speedometer and other electronics in the vehicle use the VSS speed signal. By tapping into this signal, the Stalker DSR 2X can
monitor the actual patrol car speed and use the VSS speed information to help the radar pick the correct ground speed. The radar’s
patrol car speed is still always measured by radar. The VSS simply helps steer the radar into making the right choice.
VSS Cable Installation
To take advantage of VSS patrol speed steering,
requires two cables that are provided with the VSS
Option (VSS Installation Kit PN 200-0622-00).
The vehicle VSS cable (PN 155-2221-00), should be
permanently installed by an automobile service shop
using the included installation instructions.
On the right is how the vehicle VSS cable is normally
attached (with 3 screws) to the bottom of the dash with
a metal L-bracket for convenience.
The radar VSS cable (PN 155-2178-00) replaces the
conventional cigarette power cable and can be removed
from the vehicle with the radar.
IMPORTANT NOTE: Observe the black polarity marks on the two white 6-pin VSS connectors that plug together. The two white 6-
pin VSS connectors can be plugged together with the marks in alignment or the marks opposed. Because of vehicle VSS signal level
variations, one of these plug-in positions may not provide a working VSS signal to the radar. If you observe the symptom of the
speedometer not functioning or the symptom of the radar not “seeing” the VSS signal, rotate the marks 180° and try again.
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