The idea of providing moving colour picture videophone services, better audio quality and new data services has long been one of the dearest dreams of all telecommunications network operators. Recent advances in image and speech processing, and in implementation and network technologies, are at last coming together to make this dream a reality in the very near future. Here, the author examines the principles of the transmission of television signals in a digital form, and describes how, with radio-spectrum space at a premium, the use of telecommunications lines to transmit pictures is becoming ever more attractive. >