An electronic control for the automatic transmission of a motor vehicle receives input signal in digital, analog, and pulsed form from signal generating devices responsive to operating conditions in the apparatus, processes them in accordance with a stored program and provides output signals to operate various tranducers. The electronic control is embodied in a stack of customized circuit boards. Each board is connected to a control bus (for information exchange between boards) and to an I/O signal bus (for information exchange between the apparatus and the electronic control). A connector board is connected to an electric power supply, to the signal generating devices, to the transducers and to visual display devices. A CPU (central processing unit) board protects against data loss in low/off power conditions. An input signal board employs high-speed logic circuits for measuring time length between leading edges of pulsed input signals to ascertain magnitude and rate of change of the rotational speed of certain components and actuates clutch solenoids accordingly. An output signal board embodies improved transducer-drive circuits for the clutch solenoids.