F21-4s radio remote controls best for hoist and tow truck ,easy to operate to keep workers safety. Products Application: Single hook,Single speed hoist and Hoist crane and for industrial wireless remote control use which under 9 control points etc, Brief Introduction Transmitter Size:196*65*53mm wight:320g Receiver Size:171*86*85mm weight:550g Specification: control distance: up to 100m unique code : over 4.3billon unique ID codes . temperature : -35°C-+80°C Enclosure protection class : IP65 Transmitter power: DC3v Receiver powder : AC 380v/ 36v/220V or DC12V/24V output capacity: full sealed relay output with 5 amperes Standard configuration: One transmitter ; One receiver; One 1m cable connect with receiver One operation and maintain manual . Products Features: *Four single speed push button and one EMGS button +one STOP button+one START button+ one SWITCH *control point up to 7 *With the battery voltage alarm device to cut off the circuit when voltage is insufficient. *with the Rotate key switch to guarantee the safety. *set the internal functions by computer interface *four push button can be set mutual inhibition or not . *Up ,Down ,East ,West can be set start ,close,speed up,jump strokes,ordinary etc.