The only part I see in the whole book which could possibly indicate how far a motion sensor's field extends is 5 meters. This is given range to detect a motion sensor when setting an ultrasound device to passive mode.

1. If the motion sensor can sense objects past 5 meters, then why can it only be detected within 5 meters? Even if the field does extend past 5 meters the rules normally would give dice pool modifiers equal to the range over 5 meters rather than saying it is not detectable past that range. Right? Also, if the ultrasonic field goes past 5 meters then what would be the point of detecting it? Because you would already have set it off when getting within 5 meter range.

2. If motion sensors only work within 5 meters, does that mean the ultrasound enhancement to glasses and cybereyes has this limitation as well for their ultrasonic field. I wouldn't think so due to the description, but I would like to know what others think.

As far as I know, motion sensors roll perception checks using their rating. This has standard range penalties for all perception checks. I might be wrong; I don't have the books with me - but that's how we've been playing it.

Basically I think that you need to think about what kind of area is being covered. If it is a room then have it cover that room. If you need to cover a large room then have several. They will be aimed so that they catch movement in the room but not in the doorway. That way you can alarm one room and not restrict movement in other rooms.

If you are talking about outdoors you will want to keep it shorter range by pointing it down at an angle. This will provide a way to say set off your lights when your car parksbut not set them off everytime a car drives by.

Most of the time you don't really want long range security devices. It is better to have several that can give specific data then one large one that says"In this room something bothers me!" Think function first and then set ranges.

So motion sensors only work up to 5 meters and the ultrasound vision enhancement works just like normal perception. That is the simplest way of looking at it without making too many unnecessary assumptions.

Motions Sensors come in different setups with different powers and strengths and blah blah blah. A passive ultrasound detector can find a motion sensor within 5 meters of its field. So however big the motion sensor is, you can hear it farther away than it isset up to detect you.

-Frank