Hydraulic braking systems are preferred for all-electric rolling
stock with no central compressed-air supply and consist of compact control units with a
built-in pressurized fluid supply distributed among the bogies.
It means that there are no hydraulic pipes running along the length
of the train. The Knorr-Bremse-designed calipers for mounting the power units and
transferring the braking forces to brake discs on the axles, motors or gearboxes are
extremely compact.
Stepless or step-by-step braking systems for normal service or
emergency braking and spring-operated brakes with automatic adjustment are yet another
example of Knorr-Bremse's sophisticated technology at work.
The basic philosophy adopted for the hydraulic systems is the same
as that which has been thoroughly proven in pneumatic systems over many decades.
Intelligent microprocessor control and analog converters turn the electrical signals into
a powerful hydraulic force acting either directly or indirectly, i.e., spring-applied.
New systems have been designed for special applications such as
low-floor vehicles where the low ground clearance makes the space available for
installation extremely limited. In hydraulics too, Knorr-Bremse is the perfect single
source of supply for total systems.
Electro-hydraulic 
Hydraulic disc brake