[Bob van loosen] added a remote learning circuit made from a PIC 16F84A to his Onkyo receiver – which happens to have remote buttons and a ttl control link for external devices. The PIC listens to the remote link on the receiver. By grounding a pin, it will learn the next remote command that’s received. In this case, he uses it to swap the left/right front/rear signals to gain proper speaker orientation when he switches between his TV and Computer. This would make an entertaining external dongle if you combined it with a smoke generator…