PT Primary control for EV70, EV130, EV200 & EV300 Runs unit an adjustable amount of time each hour Constant "on" and "off" capability Two wire, low voltage connection ►Download Instruction Manual PB Push button control turns on unit from bathrooms or other intermittent exhaust locations 20 minute run-time with one touch Push twice for 30 minutes Two wire, low voltage connection ►Download Instruction Manual FM Alternate primary control for EV70, EV130, EV200 & EV300 Wires to EV unit and either thermostat or furnace control to turn on furnace blower Six wire, low voltage connection ►Download Instruction Manual