A solution cheaper than the Xantech RT8 is the Xantech CC-12. The RT8 routes the signal through some active circuitry, but the CC-12 simply lets you wire up a relay to switch the IR signal to one emitter or another.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
