Older versions of the DS150i or DS151i have a jumper used to select input voltage of 12 or 24 volts AC or DC. Newer versions of the DS150i or DS151i do not require a jumper and accept either 12 or 24 volts AC or DC.
The newer version DS150i or DS151i (above) is identified by a bank of 6 dip switches; this type will accept 12VAC or DC, as well as 24VAC or DC.
Older DS150i and DS151i units (above) have jumpers located to the right of the wire plug. The 2-pin jumper to the right of the wire plug is the 24V jumper. Remove this jumper when operating at 24V AC or DC, leave in place for 12V AC or DC.