An improved scheme with vertical block allocation of embedding data into industrial quality monochrome analog pictures by modulo masking is investigated. The video signal on each scan line is sampled, and a data bit is inserted into a block of three pels by an improved modulo masking scrambling technique of the luminance level of only one pel in the block. The performance of the system proposed here is compared to that of a conventional system. The number of data bits embedded in an image for the proposed system is about 1.3 times as large as that of the conventional system. In addition the SNR of the recovered image in the new system is increased by about 3-4 dB.