A subsystem is described which enables real-time television pictures to be transmitted with very low bit rates while preserving spatial and temporal resolutions adequate for scene monitoring. The chief design constraints were to minimise the size and power consumption in an inexpensive robust construction. This was achieved by optimising the frame rate and picture resolution and by removing image redundancy using a variable Walsh transform d.p.c.m. coding scheme. A c.c.d. imager, custom l.s.i. and standard digital componets now enable a compact low-data-rate sensor and data link to be realised effectively.