User input is closely related to "Micro Cooling Fan" is the coil voltage (or current), while the pull-in voltage (or current) is a relay factory control relay sensitivity and its judgment, assessment parameters. The user is concerned, it's just a job under extreme parameter values. Control of the safety factor is the operating voltage pull-in voltage, if the relay in the pull-in value, are unreliable, unsafe, "Micro Cooling Fan" ambient temperature or in vibration, under impact conditions, will allow the relay does not work reliable. Machine design, the no-load voltage can not work as a relay voltage basis, but rather as a load coil access to calculate the actual voltage, especially when the source resistance especially big. When the "Micro Cooling Fan" with transistors as switching elements to control the coil off, the transistor switches must be in the state, 6VDC