Though I am in the telecommunications field ( software side) I am a bit confused about how everything works, though I have a high level overview. So I am stating my undestanding, so that someone can correct or fill up the gaps.
- Each home suscriber has a twisted copper pair that runs from his telephone to a cable containg thousands (why no multiplexing here and send it through a single wire??) thousands of such pairs; to the local excahnge or the central office.
- In the central office there is a hardware equipment (LTG ??) which has a lot of ports, to one of which the copper pair that runs from the suscribers telephone is plugged in.
(I hope I am correct here.)
- The central office is connected to the tandem office via trunks which I hope are a thick co-axial cable or optical fiber through which multiplexed traffic from various CO flows.
Also there is a seperate cable for SS7 siganlling, connecting various CO to TO .
There is also a switch at the tandem office.
- Now if a suscriber dials a number, the DTMF tones are resceived at the CO which has a directory (databse ???) look up. It finds that this number is at antother exchange and sends a SS7 signal to that . From there how is the trunk reserved ????
- Also how is the incoming call from a modem and telephone distinguished at the CO. Or does the modem also dial DTMF signals???
I hope someone can answer my questions.