Modular reduction gearbox

A mechanical power transmission system for controlling a valve or a louver vent, the transmission system comprising:

• an actuating mechanism for a shaft of the valve or of the louver vent, the actuating mechanism having first and second power inputs;
• a rotary motor and a rotary manual actuator coupled to the first and second power inputs, respectively;
• a rod declutching mechanism exerting a thrust for declutching the rotary motor from the first power input,
• wherein the declutching mechanism comprises a driving part and a first driven part, together forming a first dog clutch on a shaft, the driven part having a ring gear, and being coupled to the first power input by said ring gear, at least one satellite gear of the power transmission system, and a first central bore for coupling,
• wherein said driven part has a second central bore,
• wherein a rod extending through the first and second central bores is configured to push a hub of the driving part in order to perform a declutching.