The ML6421A,B Non-Spring Return Electric Linear Valve Actuators are suitable for use with low-voltage, single-pole double-throw (spdt), Series 60 two-position and floating controllers. These actuators operate standard Honeywell valves in heating, ventilating, and air conditioning (HVAC) applications. The ML7421A,B Non-Spring Return Electric Linear Valve Actuators are modulating control actuators used with control that provide an analog output of 0 to 10 Vdc or 2 to 10 Vdc. These actuators operate standard Honeywell valves in HVAC applications. An internal selector plug can be used to reverse the direction of action.