TM 9-2320-209-10-1 c. Uncoupling the Semitrailer. FRAME 1 1. Start engine. (Refer to para 4-6b.) 2. Place truck where you want to leave semitrailer. 3. Set semitrailer airbrake hand control (1) to on (down) position. 4. Set handbrake lever (2) to on (up) position. 5. Place FRONT TRANSMISSION lever (3) in N position. 6. Lower semitrailer landing gear (4). (Refer to TM for trailer). 7. Pull back on hinged 8. Push cap (8) closed 9. Place connector (6) GO TO FRAME 2 cap (5) and take out electrical connector (6) from receptacle (7). on connector (6). in stowage clamp (9) on hose support (10). 4-231