Our EA-1050 is designed for experimental aircraft. The microcontroller-based design is reliable, light-weight, consumes minimal current, and uses very little panel real estate — less than 1 sq. in. The industrial grade surface mount components used are shock/vibration resistant and provide a wide operating temperature range. The large red LED flashes for 60 seconds when alternator output voltage drops to 13V (normal output is ~14V). It then goes to continuous illumination until the condition is rectified. The flashing draws immediate attention to the condition – continuous illumination is not a pilot distraction thereafter. The LED activates when the master switch is turned on and goes out after engine start, assuming the alternator side of the master is on and alternator output is normal. Observing this should be a checklist item, as it indicates that conditions are normal and the annunciator unit is functioning prior to flight. The flashing LED serves as a reminder to turn off the master switch after engine shutdown. It’s also a helpful reminder to turn on the alternator switch after engine start. Size: 0.75″W x 1.0″L x1 .0″D, Weight, including wire: 1.0 oz. Please allow 1 week for delivery.