Subscriber Line Network
 

   The functions that are in the subscriber line network are distributor, A/D converter, multiplexer
   and concentrator. Figure 25 shows the subscriber line network.

Figure 25
 
   The subscriber  is connected  to  the  exchange  via  two-wire  pair  through the subscriber line
   network. The two-wire pair from the subscriber's premises is first connected to the distribution
   point (DP).

   One  type of  distribution  point  is  called  the  terminal  block,  has  space  for 10 subscribers
   connections. The 10-pair cable to  the  exchange is  connected  at  the  back  of  the  terminal
   block and  on  the  front  side  are  the  wire  pairs  to the  subscribers premises. The terminal
   block is protected by a case and may be placed either indoor or outdoor.

   The 10-pair cable is further on connected to a cross connection point (CCP). The CCP consists
   of a row of terminal block in the centre for connecting the 50-pair cable to the exchange and two
   rows for connecting the 10-pair cables out to the DP.

   Figure 26 shows the distribution of cable pairs to the subscriber from the exchange.
 

 
 Fugure. 26
 
    Jumper wires are laid between  the  exchange  side  and  subscriber  line  side  terminals blocks
   to the subscriber wire pairs with the wire pairs in the cable to the exchange.

   The  subscriber  line  can be  include  more complicated  functions  than  just  distribution,  for
   example the subscriber line may  be  digital  for  the  last  section  into  the  exchange.  Thus  an
   analogue to digital (A/D) converter  is  used.  An  A/D  converts  the  analogue signal into digital
   signal. The signal is then pass through a  multiplexing  equipment  installed  in  the  network  and
   sent to the exchange via a PCM link. This is illustrated in Figure 27 .

Figure 27
 
   Majority of the subscribers telephone lines are unused most of the time in the day. Therefore to
   dimension the subscriber network so that it can handle all subscribers calling  at  the  same  time
   would indeed be too genercus  and  uneconomical, so a  concentrator  is  used.  In  telecommu-
   nication, concentration  means that a  set number of  subscribers have  to  share  a  common but
   limited network resource. Figure 28 shows arrangement for a typical concentrator.
Figure 28
 
 
 
 
 
INDEX HOME