A differential communication bus comprising a master module and a plurality of slave modules connected to at least first and second conductors whereby to communicate between the master and slave modules. The master module comprises a driver for applying first and second voltages respectively to the first and second conductors and for sourcing and sinking currents in the first and second conductors. The driver controls a difference between the first and second voltages and a common mode value of the first and second voltages. The driver includes first sourcing and sinking current limiters and second sourcing and sinking current limiters for limiting the currents in the first and second conductors. The master module is selectively responsive to a fault condition triggering simultaneous activation of the first and second sourcing current limiters or of the first and second sinking current limiters to disable the driver.