Should a trainset become stranded in the tunnel due to a power failure, the couplers at each end of the Eurostar trainset are compatible with Eurotunnel's diesel electric locomotives, as are the brake and service connections. Eurostar's nose is computer-optimized for running in the Channel Tunnel, where pressure waves can affect passenger comfort. Traction Equipment One of the main differences between Eurostar and its TGV brethren is the introduction of a British-designed asynchronous AC drive, as opposed to the synchronous drive used until then in TGV technology. Eurostar's power to weight ratio is still the worst in the TGV family. This breaks with the earlier practice in TGV technology of feeding the front power unit from the rear through a 25 kV power cable running the length of the trainset's roof.
Advantages are lower currents, and simplicity.
The third rail pickup shoes, for 750 V operations on British soil, are found on each side of every powered truck. They number 12 total, and they retract when not needed to fit the UIC loading gauge. The former Southern Railway's third rail electrification, which Eurostar uses in Britain, uses a 50 Hz track circuit. The return traction current from the Eurostar trainsets also travels through the rails, so it is of the essence to avoid any dangerous interference between traction and signalling. In principle, this was to take care of the problem without excessively frequent circuit breaker trips.