PUC ... not sure what it stands for (peripheral ... controller?).
But on my BV8 I have two outbound IR ports (minijack style), and there is a thin black ribbon cable that goes from there to a small pea-sized black IR transmitter.
One associates the IR port to one of your AV ports, in my case AV1 has IR1 associated, and the AV1 SCART goes to my Foxtel's rear output port, and the IR1 cable to front of the Foxtel where its IR receiver is.
Similar my AV2 is associated with IR2 and I have connected my Apple TV2 here.
When you define these combinations to the AV port and associate an IR, you are prompted with a menu of pre-installed optional IR drivers (i.e. Sky for my Foxtel, and Apple Remore for my ATV2). Your small selection list can be upgraded with new options by your dealer (for a fee).
So the Beo4 sends B&O IR commands to the BV8, and if the BV8 has been switched to AV1 or AV2 (in my setup), it then translates the B&O IR command into a Sky (or Apple in my case) command and then sends that down the cable to Foxtel peripheral or the Apple peripheral.
First B&O (1976) was a Beogram 1500 ... latest (2011) change has been to couple the BL11 with the BL6Ks *sounds superb*