Thanks for the info guys.

So, if I only want to use my remote (MX-500) to control my switches, the IR543 is enough to do the trick. But if I want to add other wireless controllers (or X-10 remotes) to control the X-10 products then I would need a transciver. Did I understand that correctly?

And, every applicance or lighting I would like to control would need to have an X-10 switch or a lamp module (receivers) to work with the IR543.