Speed regulation was by rheostats and series-parallel control. The laboratory set includes "a welter of retorts, alembics, rheostats and plain, old neon tubing". The rheostats, which control all the lamps in the house, are of novel design. Around 1960, handheld rheostats began to appear. The Azimuth Co-ordinator uses four rotary rheostats housed in a large box. Serial connection of electric engines, Rheostats are excluded. For good response, rheostats must be matched to the particular cars involved.