Abstract: A digital transmission system in which an information signal is converted into digital data in response to a sampling pulse train, the digital data comprising a plurality of bits differing in significance from each other. Data conversion, such as complementing or reversing the order of the plurality of bits, is performed in integral multiples of every other sampling period and the converted data is transmitted over the digital transmission system to a receiver where it is reconverted back into the original digital data.

Abstract: The air in a bag which has been filled with a content is first removed by pressing to flatten the surface of the bag. The bag is then transported and supported in such a manner that it assumes an arc shape having a fixed curvature with which the convex surface of the bag is permitted to be opposed to the convex surface of a printing plate at a position just below said plate. Under these conditions, the surface of the bag is clearly printed. The apparatus for effecting the printing method of the present invention comprises a pressing device for pressing the bag, a printing plate mounted on a plate cylinder of a rotary letter press and detector for causing the plate cylinder to be rotatively driven and the rotation thereof to be stopped.