you will need to provide more details before anyone can answer this, if you are asking wether you can use a PC to control a TV via IR remote control yes that has been done , see
I guess the Psion PDA has no IRDA interface. It's probably an infrared interface similar to the one from HP48. There is also a program for HP28..48..and..similar to use the calculator as a remote control. https://www.hpcalc.org/