On Monday, February 17, 2014 2:41:50 AM UTC-8, T i m wrote:

We have recently gained a second set top box / personal video recorder
and they are both (technically) the same. The problem then is the two
remotes affect both units (as they are used independently).

There's no reason to replace any LEDs. You could more easily use
two circular polarizers (right hand and left hand) just like some
stereo-TV and stereo movie systems employ. This would require
filters on the receivers and remote transmitters.

Alas, reflections will complicate matters (the mirror-reflection of
such light changes the handedness...).

Many PVRs come with sockets in back for 'other' inputs than infrared,
you could switch one of your PVRs to a UHF remote (there are UHF receivers
that plug into that backpanel socket); this will generally override IR input,
and only requires you to get one of the universal remotes that has
UHF output, like http://www.x10-store.com/unlerepu.html for instance.

You might have to inhibit the IR output from the universal remote (black tape?).