The design of a digital encoder that will be used for connecting conference television signals to an experimental optical fibre is presented. The signal is transmitted as 4-bit words at 11 megasamples per second. The encoding makes use of psychophysical properties of human vision, but is not strongly dependent on picture content. Under normal viewing conditions, the only degradation in the received picture is a little blurring of sharp vertical edges. Transmission error rates of one per 106bits are hardly noticeable