The left and right brake pedals are connected mechanically to the Brake Transmitter (transducer) on the FO rudder pedal mechanism.
Image property of David Cheilan
XMTR UNIT BRK PEDAL (P/N C20 215000)
Pinouts
Right Brake H/P(wiper)/Y
Left Brake K/B(wiper)/V
Reference ASM 32-42-01