The motor revolutions are defined by measuring the reproduced voltage (EMP) and corrected with a pulse width modulation to the motor. The actual speed is prescribed by a speed reference counter, which may count in regular steps up and down between 0 and 127 at maximum. So acceleration and deceleration are really linear and independent from load and motor parameters. Thanks to this unique control system all problems regarding model train speed are solved. Each engine is programmed to its individual top speed. Each speed value is kept independent from load. Trains may depart in ramps, where they started to glide up to now (practical experience on 0 - and I - layouts).
Speed control provides still another very practical advantage. Because in the automatic mode during braking a determined number of speed steps in determined time steps are run through, this results in an exact distance to stop the train in signal mode. So every train may be programmed to its own stop position , that is kept load independent by principle. So railcars may stop at the platform meanwhile engines proceed to the signals, in climbings and falls, with or without waggons.
For the installation into engines with DC motors no special arrangements are needed. But first check the motor for easy departure at 1 to 2 volts and for idle current being below 200 mA. Else collector and brushes have to be cleaned or even replaced.
AC-Motors with coils instead of magnets do not produce EMP (electromotive power), so they must be converted to DC operation replacing the field coil by a magnet. There are a lot of conversion sets available. But use only spare parts, if sets contain expensive decoders you cannot use for ATL control. The behaviour of changed motors will be much better and speed control is only possible this way.
After all, our modules may also be operated without automatic speed regulation. If so, you should use the programmable speed curve, where you can adapt your motors to the needs (motor power on lowest speed step, top speed, linearity, and so on).