It consists of hydraulic pump/ oil tank/ pilot relief valve/ equalizing valve/ hand-operated  direction

 valve / pressure gauge and bimetal thermometer etc. 

This power pack is driven by electric motor, then the oil transfer from pump to relevant  valve, 

operate hand-operated direction valve to change the flow of hydraulic oil, change  rotating 

direction of hydraulic motor, realize pulling in rope and paying out rope. If accident,  the oil 

pressure exceeds system pressure, Pilot relief valve unload, has function of safety  protection.