The HLT7000BL High Torque Brushless Digital Servo - Designed and Manufactured in Australia. Unbreakable fully billet casing, waterproof *, 15T gear teeth, heavy duty metal gears, quality core metal motor, smart digital signal controller with Led status signals for diagnostic, quick disconnect servo lead, automatic shutdown if no RX signals present.  Servo requires 3 to 5Vdc square wave pulse. Pulse duration is from 0.9mS to 2.1mS with 1.5mS as center. Servos can be operated within a 7.4V-8.4V. range. The Black wire is 'ground', the Red wire ( center ) is 'power' and the third wire (white) is 'signal'.

*Servo is splash- and water-proof, but submerging is not recommended.
 
 LED Signal Status:- Green Flashing: No Radio Signal / Inactive- Red Flashing: No Radio Signal / Low Battery / Inactive- Green ON: Active- Red ON: Low Battery voltage (Below 6 Vdc)See specs here :
 
http://www.hilantronics.com.au/images/HLT7000BL/HLT7000BL.pdf