Application of pulse-code modulation to an integrated telephone network. III. switching

For Parts I and II see abstracts 1963B13778. Possible methods of connecting subscriber lines to a pulse-code highway are discussed. The four-wire solution of subscriber line equipment is shown; it consists of two transformers, speech amplifier and transmit and receive gates. The concentrator has only one function as regards switching, that is to establish connection between subscribers and channels. All logic functions are performed in the exchange which controls the concentrator by sending to it connect and release orders. Two variants of switching of multiplex highways in the exchange, i.e. space switching and time switching, are explained. Synchronization equipment which puts all incoming signals into appropriate time intervals is described. Traffic improvement by rearrangement of existing connections, when required by a new one, is evaluated; this method helps to avoid internal blocking due to time positions engaged only at one end. Models of the concentrator and the exchange are briefly described.