Patent US 3,940,593

An electronic process controller is disclosed having analog circuitry for generating an analog control signal, a digital memory for generating a manual control signal and digital circuitry for sequencing of the analog functions. This controller provides drift-free manual control in the manual control mode, tracking of the process control signal in the automatic mode to allow bumpless transfer from automatic mode to manual mode and output ramping to allow bumpless transfer to and from direct digital control mode.