Brooks Instrument 5866M - Manual (Page 17)

Brooks Instrument Model 5866 Pressure Controller
2-6
2-13 Optional Valve Return
Units manufactured after January, 1992 with a Normally Closed valve can
be configured so the valve current can be returned to the power supply on
a separate line. This is recommended if the power supply lines are longer
than 10 feet. The feature is enabled by connecting Pin 3 of the D-Connector
to power supply common with a separate lead and moving Jumper J3 to
the Position a.