For that, he developed an IR ... module found in the cable box to decode the signals from the remote. With a few MOSFETs, this signal is fed over a three-position screw terminal to the transmitter ...

[Xtropie] used a pair of inexpensive 433 MHz RF modules ... IR sensor to make sure there were no conflicts. In fact, if you removed the sensor, you could reuse it and connect it to the IR transmitter.