"Tiny Cooling Fan" is a relay allows loading of voltage and current. It determines the relay can control the size of the voltage and current, can not exceed this value, otherwise it is easy to damage the relay contacts. Edit relay test test this paragraph "Tiny Cooling Fan" contact resistance with a multi meter resistance profile, measuring normally closed contact with the fixed point resistance, the resistance should be 0, (with more precise way can be measured contact resistance 100 milli ohms or less); and normally open contact with the fixed point of resistance is infinite. It can be distinguished that are normally closed contacts that are normally open contacts. "Tiny Cooling Fan" available multi meter measured coil resistance R × 10Ω range measuring the resistance of the relay coil, the coil in order to determine whether there is open circuit.