On Tue, 25 Jan 2005, Dave VanHorn wrote:

>> Nope. I recently saw an episode of Fifth Gear where they were testing
>> radar and lidar detectors, and one of the major gripes was the lidar
>> detector going off in front of certain grocery stores.
>> 
>> Most of the grocery stores in my area us IR (I've seen them opened).
>
> Passive IR won't set off a lidar detector.

They are not passive. The radar type openers have a poor record in 
certain areas and the ir type is less expensive to make so ...

f.ex. most single-sensor radar door openers refuse to open the door if 
you approach it from the side and close enough, if they are adjusted to 
open it right if someone approaches straight from front. I tend to walk 
fast and I have to wave my hand in front of me (or above me) to get the 
doors opening in time even head on. The active ir type is not so 
affected by these problems (it does not rely on object motion and it has 
a lens that fixes the can't-see-near-the-door problem). Also many 
passive (PIR) ir sensors for door openers have reduced range for people 
coming in from the cold wearing suitable clothing.

>> But that's the point: the signal LOOKS like it comes from a Lidar, which
>> is why Lidar detectors are triggered. Anything that sets off a Lidar
>> detector has the good potential, if strong enough, at interfering with a
>> Lidar gun.
>
> Primitive ones maybe. How likely is it for your video sender to interfere 
> with my cordless phone? They are both in the 2.4 GHz band.  Not at all, since 
> my cordless is direct sequence spread spectrum. I just don't "see" your 
> signal.

You don't want to know. Phones, microwaves and 802.11 gear all share the 
same band. You have white bands on your video link ? Just wait until the 
802.11 retrains and leaves you alone (since you are jamming it too 
with the video link).

Peter
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