Synchronization of a PCM Integrated Telephone Network

To compose a telephone network with low transmission loss without cumulative increase of quantizing noise, it is desirable to accomplish both transmission and switching with PCM modulation. Such a system, called an integrated telephone network, requires synchronization of incoming signals arriving at each exchange to the local timing pulse generator controlling a time division switch of the exchange. In the synchronization method described in this paper-the equational timing system a local oscillator of controllable frequency that drives the local timing pulse generator in each exchange is controlled by making reference to the phase differences between incoming signals arriving at the exchange from the other exchanges and incoming signals arriving at the other exchanges from the exchange. This synchronization method permits the minimun storage capacity of the buffer memory indispensable for compensation of the junction-delay variation, indefinite enlargement of the network and multiplication of its complexity, and invulnerability to the consequence of failure of one or more junctions or timing pulse generators in the network. The phase differences between the local timing pulse generators of exchanges in the network, the stability of the network applied with this synchronization method, and an example of the equational timing system are discussed.