The Brompton Electric is a pedal-assisted bicycle (also referred to as Pedelec or EPAC).
The electric motor is powered by a rechargeable battery and gives extra assistance until 25 km h/15.5mph, whilst the rider is pedaling. The amount of assistance depends on certain factors: the speed of the bike, the pedal speed and the power input into the pedals.
The bike has an in-built speed sensor and torque & RPM sensor in the bottom bracket to measure these factors accordingly.
Finally, the selected assistance mode used whilst riding (0=no assistance, 1=low, 2=medium or 3=high).