An electric trolley bus is one in which power is drawn from overhead electric wires via the pole (also called pantograph). The voltage required for moving a bus is generally 600 DC (direct current). 

This electric trolley bus with 3-axle was called the Q1 and was introduced during the year 1948 and plied in London until the early 1960s. With a lower seating capacity of 30 and upper seating capacity of 40, this trolley bus model could transport more than 70 plus passengers.

A number of these buses were also exported to Spain (125 nos.) and they operated there until 1979.