The AA-12 ADDER A (R-77) is an medium range, air-to-air, active radar-guided missile. It is a high supersonic solid fuel rocket with laser proximity fusing. For guidance, the missile utilizes an inertial system with mid-course updated and an multi-function doppler-monopulse active radar seeker for terminal guidance, beginning at approximately 20 km from the target. This active radar seeker also gives it the capability for an active "fire and forget" mode at closer ranges. It can be utilized by the MiG-21-93/MiG-29/31/35, Su-27SM/30/33/34/35/37/47, Yak-141 and the J-10B . The R-77 is roughly equivalent to the American AIM-120 AMRAAM missile.

Source: http://en.wikipedia.org/wiki/R-77_(missile)