How does Insteon work?

["Monte Castleman" <mdcastleman@xxxxxxxxxxxxx>]

I'm an X10 veteran getting started with Insteon equipment. Just wondering
how the protocal works. Suppose I have a tabletop controller linked to a
lamplinc "L". If I hit the on button, does it work like X10 where the
transmitter says simply "Button 'B' pressed", then the lamplinc gets the
message and thinks "Button 'B' has been pressed, that means I'm supposed to
turn on." Or does it work the opposite, where the transmitter knows what
devices are linked to it, and sends the order "Lamplinc 'L' turn on" when
you press button "B".

Also, is there any real difference between an Insteon primary link and
Insteon scenes? I'm assuming no, and that this distinction is a holdover
from X10 days.

About how many Insteon devices can you add to a small house before they
noticably degrade X10 performance. 5? 10? 20? Is there a suggested limit per
circuit?