x10 and other systems for remote controlled lighting

I have heard about the x10 system for light and appliance control, and I am interested in building my own, but I haven't been able to figure out one part. They have a module which replaces the standard toggle switch which controls regular ceiling lights. Now, when I checked my toggle switch, there are two wires that can be connected or separated by the switch. Would the control for that x10 switch be in series or in parallel with that switch? What happens when it closes its switch and turns on the light? If it is in series shouldn't it greatly reduce the brightness of your lights? If it is parallel, did you just short its power supply by closing the switch? How would it work?
thanks

I haven't used that module, but the one I have makes a big clunk when turning on. That tells me it has a relay inside. If the light switch module is like that, then the relay contacts work just like the light switch. If it does not replace the switch, then it will be in parallel with it.

beenthere said:

I haven't used that module, but the one I have makes a big clunk when turning on. That tells me it has a relay inside. If the light switch module is like that, then the relay contacts work just like the light switch. If it does not replace the switch, then it will be in parallel with it.

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My question is, if it switches with a relay, when the circuit is closed, you go from and open voltage of 120VAC to 0VAC, how do you then control the relay with 0VAC?

While voltage between the switch contacts may go to zero when they close, the voltage measured to AC common remains at 120. The module gets it's power from the AC hot and common lines. Closing the switch just completes a circuit.

beenthere said:

While voltage between the switch contacts may go to zero when they close, the voltage measured to AC common remains at 120. The module gets it's power from the AC hot and common lines. Closing the switch just completes a circuit.

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I only have two lines in my wall switch, and they are connected when the switch is closed.

Does that mean your switch is not in a box where three wire colors are present? There should be a black wire carrying 115 VAC hot, a white with AC common, and a green or bare wire that is ground. The switch makes a closure between the black from the distribution box and the black to the lamp socket.