Digital techniques are discrete techniques and they have been applied to automatic telephony since its invention. The technology for the extensive application of digital switching and marriage to similar transmission techniques and services dependent thereon are emerging as economically viable. A clearer understanding of the principles of digital switching is now perceived. Definitions are given to such elusive terms as digital switching, multiplexing, buffering, time and space stages, time shims, time slot interchange and BORSCHT. At this stage in the development of digital switching, as we are about to take the last steps to achieve integrated end-to-end digital networks, it is appropriate to pause and review the milestones that have illuminated the way. Like this entire issue, this article serves as a reference to the state-of-the-art and how we got here.