(1) allow power Pm: allows the LED at both ends was to the DC voltage and its current product of maximum value. Exceeding this value, LED heat, damage.
(2) maximum DC forward current IFm: allows the maximum DC forward current. Exceeding this value can damage the diode.
(3) the maximum reverse voltage VRm: allows the maximum reverse voltage. Exceeding this value, light emitting diode can be penetrating damage.
(4) work environment topm: light emitting diode working ambient temperature range. Below or above this range, light emitting diodes will not work, efficiency is greatly reduced.