Feasibility studies of synchronised-oscillator systems for p.c.m. telephone networks

Two important classes of linear control system for pulse-code-modulated exchange-oscillator synchronisation are described. These are known as `single-ended¿ and `double-ended¿ systems. This paper extends the knowledge of the stability and steady-state frequency for the single-ended system, and derives the corresponding information for the double-ended system. Both systems have discontinuous phase comparators, which can cause undesirably large phase differences in the steady state. This is known as `wrong-mode operation¿. Existence conditions for such a wrong mode are used to detect and eliminate it. The stability criteria include the effects of filters in the error-signal paths. These filters, the line delays and the operating mode will all affect the steady-state frequency of the single-ended system, but not of the double-ended system. The latter is thus more likely to be used in practice. The paper shows that a synchronous integrated p.c.m. network is completely feasible, although the economits of such a system have yet to be proved.