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Unquestionably Confused

On 8/10/2016 3:06 PM, wrote:
On Wed, 10 Aug 2016 08:20:58 -0500, Unquestionably Confused
wrote:

On 8/10/2016 8:11 AM, Pat wrote:
On Wed, 10 Aug 2016 03:09:05 -0400, wrote:

I've always wondered how they work, and
why they dont detect cars going the opposite direction.(I assume they
work on radar). ???

Yes, they work on radar. Cars going the opposite direction DO get
detected, but they show up as going a negative speed. The built-in
software just ignores those signals and displays only positive speeds.

Interesting.

Seems obvious that they must employ a unique radar frequency as
oftentimes my Valentine One (a great radar detector) doesn't utter a
sound even though it's set to report ALL threats.

The silent treatment occurs with a fair number of the portable "Speed
Alert" trailers the police move around to provide a courtesy warning to
motorists as well.

Possibly LIDAR instead of Radar

Doubtful as the Valentine One picks up LIDAR/Laser as well. Trips
everytime I run through a toll plaza where the cameras are equipped with
IR Illuminators to light up the plates at night.

One explanation I read was frequencies of the mobile units, since they
aren't used for enforcement, per se, are not calibrated/recalibrated and
the detectors won't pick them up.

No attribution was provided with that explanation so I rather doubt it
for that and several other reasons.