The Car Speed Profi introduced in 1981 was the second ESC from CS Electronic but comparing with the older Car Speed Super this one was designed as real race ESC and a 2nd generation design. This means not one but three large powertransistors were used for motordrive and one additional powertransistor for dynamic brake. A relay activated at endpoint of braketravel provided a fixed speed reversefunction. A BEC unit was used as well for powering receiver and steeringservo. For lowering the weight of this ESC CS went with an aluminium plate as heatsink for the powertransistors and a heatshrink instead of a heavy case. This also is the route most European ESC manufacturers were going for lower weight that time.
The second generation of ESC tried to overcome the handicap of their predecessors. Comparing with mechanical speedcontrols early ESC had a much faster response time but also had very large voltagedrop what means the motor had less revs and power at full throttle. To overcome this situation there were two solutions.
The first one as used by British and Japanese ESC mostly was using an additional speedrelay for bypassing the voltagedrop of about 0.7-1V of the powertransistor. Demon Products from Great Britain was one of the first manufacturers using such speedrelay at their Demon 2D ESC.
The second solution was using not one but multiple number of powertransistors in parallel. This meant less burden for each transistor and a lower voltagedrop overall. This is the design as used by this CS ESC. More informations to find at our coming Special on “Vintage” ESC.