A two-transistor gate for time-division switching

A bilateral balanced solid-state gate, suitable for use in a pulse amplitude modulated time-division telephone switching system, is described. The gate, consisting of two junction transistors and a pulse-transformer, is capable of handling the currents required to produce a low-loss connection when operated for two microseconds every one-hundred twenty-five microseconds. The need for such gate arises with the extension of time-division techniques from their well known applications in multiplex transmission to their less obvious but equally worthwhile applications in the switching of transmission paths in a telephone office. The two chief problems that time-division switching raises are in keeping track of associated pairs of lines while waiting for their assigned time slots, since sampling is no longer in unchanging sequence, and in providing low loss bi-directional sampling within a time slot to permit two-wire operation without expensive analogue pulse amplification in the common medium. This paper describes a simple gate that solves the latter problem.