Transmission System

TRANSMISSION SYSTEM

I.TELEPHONE TRANSMISSION SYSTEM

          A telephone transmission system is a pair of wires connecting two telephone or data modems together. A more practical transmission system is comprised of a complex aggregate of electronics equipment and associated transmission medium, which together provide a multiplicity of channels over which many subscriber’s messages and control signals are propagated

           

            In general, a telephone call between two points is handled by interconnecting a number of different transmission systems in tandem to form an overall transmission path between the two points. The manner in which transmission system are chosen and interconnected has a strong bearing on the characteristics required of each system because each element in the connection degrades the message to some extent. Consequently, the relationship between the performance and the cost of the transmission system cannot be considered only in that system. Instead, a transmission system must be viewed with respect to its relationship to the complete system.

            To provide a service that permits people or data modems to talk to each other at a distance, the communications system must supply the means and facilities for connecting the subscribers at the beginning of a call and disconnecting them at the completion of the call. Therefore, switching, signaling, and transmission functions must be involved in the service. The switching function identifies and connects the subscribers to a suitable transmission path. Signaling function supply and interpret control and supervisory signals needed to perform the operation. Finally, transmission functions involved the actual transmission of a subscriber’s message and any necessary control signals.