Trunk cable enters exchange in Ďpití.
This area is flooded
in many BT exchanges because of poor maintenance.
Every line eventually connects to the
frame in the BT exchange.
There is surge protection here, so however much you hate BT, you canít just put your phone line in a socket
and blow up their
exchange, nice though it would be.
Contain a variety of logic, including
units that are shared
to interpret what number is being dialled. Audio is digitised at this point and
internally in the exchange is packet switched, just like a computer network. This is where DSL is installed. If
DSL packet switches data
across the exchange backplane, it is questionable how many lines could be supported with DSL without an
exchange upgrade. Does
anyone know about this?
External cables are often filled with
compressed air or
grease to protect from water seepage. In reality, many such cables in the BT network
have long since been
ruptured or depressurised.
Cable joint. These used to be made of
lead and it was a real craft to construct one. Now, these are plastic cans, usually with IPC crimp connection between
wires. These occur frequently
throughout every old fashioned telephone network. This is where water can cause
unwanted line capacitance, crackle etc. Sometimes, BT engineers donít even bother with proper joints, they just tape the