Hired-Hand System 500 Power Curtain Controller - Manual (Page 10)

System 500™ Power Curtain™ Controller 8
6.2.2.6. Cycle Time Adjust
This potentiometer is used to set the time delay between curtain
operations. If cycle time is set for 3 minutes, then the curtain will
move every 3 minutes if needed. The curtain will not move between
cycles, unless it is manually moved.
6.2.2.7. Variable Speed Fan (Enhanced Version Only)
6.2.2.7.1. Variable Minimum Adjust
If you have the enhanced version of this controller, this
potentiometer controls the minimum speed of the variable
speed fan. For example, if the variable minimum is set at
50%, the fan will never run below half speed.
If you have the basic version of the controller, these switches
are not installed.
6.2.2.7.2. Variable Span Adjust
This setting controls the temperature difference between the
minimum speed temperature setpoint and the maximum
speed setpoint. In other words, this value represents the range
of the variable speed fan.