A digital positioning system has a carrier in the form of a belt with a work surface and arrays of first and second conductors extending under that surface generally parallel to one another, each second conductor being spaced close to a first conductor to define a narrow gap between them. A voltage source applies a potential difference between the conductors to produce electrostatic fields which can attract and hold a substrate to said carrier work surface. Sensors are provided to enabling the longitudinal and lateral positions of the belt to be monitored to produce control signals to shift work elements operating on selected locations of the substrate at successive work stations to compensate for unwanted movements of the belt.