What was found
FLT 4905 - ROC - LEFT MAIN GEAR INDICATION, NO GREEN DOWN AND LOCKED. TRANSIT LIGHTS DID ILLUMINATE. FOLLOWED QRH PROCEDURES. VISUALLY SAW GEAR DOWN. COMPLETED A TOWER FLY BY FOR VERIFICATION. DECLARED EMERGENCY, LANDED WITHOUT FURTHER INCIDENT. INSPECTED WIRING AND SWITCHES, FOUND CANNON PLUG CAME OFF SWITCH ASSEMBLY. RECONNECTED AND ALL INDICATIONS NORMAL. (M)