I have an IR543 (X10 RF interface) for controlling the lights in my media room. But it stops working when my HP LC3200N LCD TV is on, due to IR interference. Up until today, if I wanted to adjust the lights using my universal remote, I had to turn off the TV first.

But I also discovered by testing that if the IR543 was completely isolated from visible light emissions from the TV, it remained operational even if the TV is on, and even if the IR543 is still close to the TV. So I considered ways to isolate the IR543 from the TV's light emissions. I read about the PAC IR-X, how it operates at either 40KHz or 53KHz. Hmm. The IR-X might be able to ignore the LC3200N's IR emissions while the IR543 is too cheaply engineered to ignore the same off-frequency IR emissions.

I ordered a PAC IR-X IR extender--$30 including shipping.

Received the IR-X today and hooked it up. Powered it with a spare AC adaptor that outputs 11V DC. Mounted the IR extender's IR sensor on the front of my AV receiver. Taped the IR extender's IR emitter on the front of the IR543 with black electrical tape. (The black tape is sufficient to isolate the IR543 from whatever light (visible and IR) coming from the TV.)

Problem solved. Now my LCD TV and my IR543 cooperate.

This might also work for some plasma TVs which apparently have the same issue with the IR543.