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pre‐set distance in order to create a magnetic field or induction loop. Once a vehicle is in the
intersection, the loop or circuit becomes closed and alerts the computer to take a picture.
In some states, tickets are issued to the car's owner, no matter who's actually driving. In this case, the
red‐light camera only needs to photograph the vehicle's rear license plate. In other states, the actual
driver is responsible for paying the ticket. In this case, the system needs a second camera in front of the
car to get a shot of the driver's face.
How speed cameras work
There are several types of fixed‐position speed cameras used, including radar, laser, induction‐loop, and
photo‐based.
Radar‐and laser‐based cameras are typically mounted near the road and transmit a short‐range signal
across the lanes monitored. Since this signal is transmitted across the road instead of down the road like
with many handheld systems, detecting them in time is critical.
Another technology used is an induction‐loop system. This type of system utilizes wires buried just
beneath the surface of the road to trigger a computer that calculates speed between the two points.
Photo‐based systems take two sets of pictures of all passing vehicles between two separate fixed
locations. Both sets of photographs are date and time stamped, which enables the system to calculate
average speed between the two locations.
Fixed‐speed cameras can also be set up to monitor one to four lanes of traffic in the same direction. To
achieve this, a sensor is installed in each lane, and a wide‐angle camera lens is used to photograph the
vehicle that is speeding.
Interpreting alerts
Although PASSPORT iQ has a comprehensive warning system, only experience will teach you what to
expect from your detector and how to interpret what it tells you. The specific type of radar being used,
the type of transmission (continuous or instant‐on), and the location of the radar source affect the alerts
you receive.
The following examples will give you an introduction to understanding PASSPORT iQ's warning system
for radar and laser alerts.
Note: This guide applies to alerts in Classic mode. For details on how to set your alert tones, see
"Setting Your Alert Tones."
Alert: Detector begins to sound slowly, then the rate of alert increases until it becomes a solid tone. The
signal meter ramps accordingly.
Explanation: You are approaching a continuous radar source aimed in your direction.
Alert: Detector emits short alerts for a few seconds, then falls silent, only to briefly alert and fall silent
again.
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