naim set up question

I have the nac 42 with nap 110 and snaps.

I do not understand how the snaps fits into this system. The preamp seems to power up with just the output attached to the input of the amp. There is no 120v power cord for the preamp. I thought the snaps was a separate power supply for the pre-amp. The system works well without the snaps in place.

Any advice will be appreciated

Andy