Abstract: A transmission unit for bicycle brakes consisting of a single operating force input (10, 12) connected to a force multiplier (14) which distributes said multiplied force between two operating force outputs (16, 18) via a differential which equalizes the two operating force outputs while giving preferential motion of one of the outputs in the phase of motion prior to the full equalization of the multiplied operating force. This unit allows a single brake cable (12) from a control lever (10) to connect within the unit to a cam actuator follower which transfers this single operating force by means of a ratio modulating cam lever (26) which incorporates a guide pulley which moves via a fulcrum pivot axle (28) located between the cam structure and the guide pulley structure. This mechanism is combined with a cable (16, 18) which is looped around 180.degree. of the guide pulley and which exits the unit in parallel paths in a direction of opposition to the motion of the cam structure via the pivot axle described.