The Synchro Cannon is an advanced Reflex weapon which utilizes a synchronized energy beam that is capable of disintegrating large numbers of armored targets.
The Jupiter Division had been testing a small-scale version of the weapon, which was self-propelled as a hovercraft, enabling it to move about on uneven terrain. The operator sat in a small bubble-canopied command module on the side of the weapon's barrel. This unit ended up on Earth when an advance scout group from the Expeditionary Fleet was destroyed by the Invid. Sue Graham of the 36th Squadron attempted to hide the Synchro Cannon from the Invid, but it was destroyed by Scott Bernard's resistance group to prevent it from falling into enemy hands.
The largest-scale Synchro-Cannon ever built was constructed into the forward superstructure of the SDF-4.
Episode 83 - "Reflex Point"