Hiya!

Well, let's say the signals are a sample of an analog signal rectified and sent to a multivibrator to turn them into a pulse representation. The pulses are then sent to a pin to a PIC. I don't have any specific chips in mind, but I'm thinking maybe a PIC12F675.

The signals come from multiple sources. Let's say three. So, I would use three pins from the PIC. Then, when the PIC detects a signal, it is supposed to do some processing and then re-route the signal via a separate analog switch. The PIC would control the analog switch.

So as different signals come along from different sources, then the PIC is supposed to prioritized them based on which source the signal comes from. So, if the PIC is processing a signal from a 2nd priority source and a 1st priority signal comes along, it is supposed to stop what its doing and process the 1st priority signal.