x10 wireless works better with timer plugged in?

["peter" <nospam@xxxxxxxxxx>]

I have a set of x10 wireless remote like this:
http://www.smarthome.com/includes/showimage2005.asp?img=/images/4000_nbig.jpg

I use it to control two lamps (incandescent bulb), using dimmer modules, in
my TV room. For some reason, sometimes the system is not reliable -- the
lamps stop responding to the remote. New batteries didn't solve the problem.

What does solve the problem is to plug in an x10 timer like this (mine is
black and is older radioshack style):
http://www.smarthome.com/includes/showimage2005.asp?img=/images/1100xnbig.jpg

When the timer is plugged in, the lamps responds to the remote reliably.
Why? Does the timer act as a signal relay?