Throttle control lever sends reverse thrust command independantly to EIU, ECU. EIU closes inhibition relay switch and then only ECU deploy command goes through to hydraulic control unit which activates actuators through respective hydraulic system. In case of IAE, ECU is called EEC. Apparently it needs 28V DC. That is why REV inop.
Last edited by vilas; 7th Aug 2013 at 14:27.