| Analog
local loop interface |
| Loop
current used for signaling & message |
|
|
| Digital-lines
to |
|
| ISDN
central office |
|
|
|
|
|
|
|
|
|
| per
trunk signaling |
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| in
local loop: |
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| - long setup time |
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| - hacking easy |
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| - voice grade
circuits |
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| - interference
& cross-talk |
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| sensitive |
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| - expensive |
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| Analog-line |
