Nothing fancy… no microcontroller, no firmware. Just a 555, a TMS5330 infared decoder (but almost any decoder should work), a long cable and an IR LED. That’s all.
I’ve used three of these circuits and I’m now able to use almost any remote in any room.
The trimmer on the circuit change the IR carrier frequency. It should be 38 Khz, but my appliances likes more a carrier of 42-43 Khz.
This is the schematic: