How does the Nagra PL-L switch between 115v - 220v

Trying to find out if the PL-L switches between 115 and 220 on it's own or is there a switch inside.

Hi I just read my owners manual. No switches or anything. Just supply the ACPS power supply with a input voltage of 90-132 or 180-264 at a freqency of 50-60hz.