==== Design and Development of Commercially Viable ISDN Customer Premises Equipment ====
By P.Samar 
=== Abstract ===
The thesis presents the work done towards the design, development and testing of a cost effective voice/data terminal for ISDN. The terminal provides both digitised voice and data connections simultaneously. These connections can be routed to a single user or to two different users. The terminal facilitates data rate of 128kbps in the absence of voice connection and 64kbps when a voice call is active. The terminal has been developed as a PC add-on and is interfaced to a handset and a handsfree speaker system for voice connectivity. This card has been developed using the Industrial Standard Architecture (ISA). The card was tested on a 286 machine and is upward compatible. 

The project also includes development of a Network terminator (NT) which is part of the customer premises equipment (CPE). This NT has been modified to enable the testing of the Terminal Equipment (TE). The modified NT facilitates the testing of the lower communication layers of TE. Activation/Deactivation of the four wire S-interface is done by NT with a request from TE. 

The terminal has also been tested for multipoint access by connecting two terminals on a bus network at the S-interface reference point. Medium access is implemented using Carrier Sense Multiple Access\Collision Detect (CSMA\CD). CSMA\CD has been implemented using both hardware and software. The thesis also presents a method of implementing Data  Link Layer (DLL) for error control in the 64kbps information channels called B-channels. 

The system software is layered in accordance with the standard OSI 7 layer model. The communications layers which comprise the lower three layers have been implemented in accordance with the ITU Q ANd I series recommendations. A number of applications are provided for text/data communication. These include mail service, PC-to-PC file transfer and text mail. The voice mail application provided by the terminal enhances voice communication. Since the signaling information is transmitted on a different channel, a number of supplementary services like caller address identification, call waiting are also provided to the customer. 

A front-end software has also been developed to help the user navigate through all the applications. A prototype of voice/data terminal for ISDN has been developed with a view to make the product commercial. 
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