On Wed, 10 Aug 2016 16:13:25 -0400, wrote:

On Wed, 10 Aug 2016 09:41:16 -0500, "cowabunga dude"
wrote:



Unquestionably 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.

Those speed detectors always show my vehicle is going 3 mph slower than my speedometer.

because your speedo, like most, is inaccurate.. Perhaps your tires are
undersized??
That could be it, or it might be working as designed. I believe that
cars in the US must have speedometers that are accurate to within
minus 0% and plus 5%. I don't recall the exact number, but the idea
is they can allowed read fast but never slow. If that is true, I
would think the average speedometer would read a liitle fast. At 60
mph, a designer working with a + or - 2 mph device would set it to be
2 mph fast thus turning -2 to +2 into -0 to +4 with an average of 2.