Abstract: Binary signals from picture elements arranged in rows and columns of the subject copy are successively applied to a group of shift registers and suitably time-delayed under the control of clock pulses so that the signals from reference picture elements for each object picture element simultaneously enter two logic circuits provided for a high and low scanning resolution. The logic circuits calculate predicted values for each object element following respective prediction functions. That circuit for the scanning resolution used delivers the predicted value to an exclusive OR gate also supplied with the actual signal from the same object element. Each time the gate determines a discord with the prediction, a coder delivers coded serial signals having predetermined variable lengths dependent upon the number of pulses counted up to that time by the coder. Also by referring to a picture element or elements farther distant from the object element, generized prediction functions are disclosed.