™ Multiplexing Application-Cont

Switched Analog Services With switched lines, caller dials a number and call is conveyed to a series of switches at the exchange The switch connects two lines for the duration of the call

Analog Leased Service Offers customers the opportunity to lease a line, sometimes called a Dedicated Line Dedicated line is permanently connected to the other customer Although the connection still passes through switches in the exchange, the customer experiences it as a single line because switch is always closed No dialing is needed Conditioned Lines o    Another service offered by the carriers o    Conditioning means improving the quality of a line by lessening attenuation, signal distortion or delay distortion o    Conditional lines are Analog but their quality makes them suitable for digital data communication when connected to Modems Analog Hierarchy o    To maximize efficiency, telephone companies multiplex signal from lower BW lines onto higher BW lines o    In this way many switched or leased lines can be combined into fewer but bigger channels o    FDM is used for analog lines