ISDN tools: intelligent terminals
John Ronayne · 2023
It has already been indicated that the digital communications network is being introduced for reasons other than the desire to implement the ISDN. PCM time-division multiplexing (TDM) was first introduced to reduce costs and provide improved transmission properties, but it was very soon realized that the combination of PCM TDM transmission and switching with SPC provided a more economic solution for the whole network. Hence, the integrated digital network (IDN) is being put into place for purely economic reasons. For integrated access to become a reality it was necessary for the telecommunications authorities of the world to agree on the nature of this access by defining the customer interface and the customer-to-network protocols. Having briefly defined access in terms of the communications paths from the subscriber to the network, it is necessary to describe the devices using this access and to define the boundary interface between the subscriber and the ISDN.