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How does dial-up networking work?

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NJ Roadmap

New Member
After spending ages looking for information on the internet, I have resorted to this forum - I can't seem to find any info on how an analogue call from a data modem gets routed through an exchange to an ISP (modem?) and most importantly how an ISP is able to handle 100's of calls a minute.

My theory is this (correct me if I'm wrong!):

-Analogue call from modem gets intercepted at local telephone exchange (it's recognized as a data call because of the number being dialled - from a list of ISP telephone numbers possibly?).
-**
-From here it gets transferred via the ATM network to a gateway and then to the ISP's server.

I still haven't been able to answer the question of how and at what stage the analogue to digital conversion takes place (Possibly at the ** location above?)..I remember reading an article online a few weeks ago but cant remember where!

Any info or web links would be appreciated.

p.s. I'm interested in this info because I'm writing a proposal for automatic utility meter reading possibly via a telephone network (modem on the meter dials into the utility's server)
 

aibelectronics

New Member
The transmission via the xchange is analog (since your PSTN is voice anyway). The DTE (Data Termination Equipment) process data in digital form, so the ADC conversion takes place at the modem and at all digital devices connected to the telephone network. I'm not sure if that's what you're asking for?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Originally there were things called POP's (Points Of Presence), and you had specific numbers all round the country. Back then I was with Demon Internet, and the number I dialled had SIXTEEN lines only - it was a Sheffield number, and covered a LARGE area - including Hull. This was a problem, because Hull has a private telephone system (even today), and it allowed unlimited local calls for 5p - as the Sheffield number fell within 'local calls' some idiots in Hull left their modems permanently connected, reducing the 16 possible connections. The eventual action taken to prevent it was to ban Hull residents from those numbers. I don't know where in Sheffield I dialed into, but from Sheffield there was a 64Kb line that transferred the data from the 16 modems to Demon's servers down south.

This was how all domestic Internet connections were done.

Demon then introduced VPOP's (Virtual Points Of Presence), I believe Demon were the first to do so? - and this is what still happens today. Essentially it needs a MUCH larger infrastructure, if I remember correctly it was one of the large electrical power companies?, and they ran high speed network lines all round the UK - one method was a robot which ran along the HV pylon cables and spun a fibre-optic cable around them. This allowed them to build a country wide network very cheaply - no digging roads up or anything.

So your call now went to just one number no matter where you were, and your local exchange transferred it to the power companies network system, then from there to your ISP's servers (in my case back then, Demon).

Demon obviously had to pay for the use of the infrastructure, but no longer had to build and maintain small banks of modems around the country, and pay for poxy 64Kb lines to their servers.

I rather suspect that you haven't really looked into the logistics and costs of what you're proposing? - if it was easy (and cheap) it would have been done years ago!.
 

Phasor

Member
NJ Roadmap said:
p.s. I'm interested in this info because I'm writing a proposal for automatic utility meter reading possibly via a telephone network (modem on the meter dials into the utility's server)

Not sure if you're aware, but this sort of system has been in use for years (at least in Australia). What (more precisely) are you trying to do?

We (as an electricity distributor) have modems on the meters of all our large customers (> 400A) and those customers whose meters are difficult to access. The majority of those operate over the cellular network (rather than a land-line, as land-lines are more expensive for our purposes)

Unfortunately, I can't fill you in on technical details of this sort of system (since I don't work the metering section).
 

NJ Roadmap

New Member
I am aware of that, I am trying to assess which method of data collection is the most feasible and economical in the UK:
1.Landline
2.GSM/GPRS
3.RF walk-by or drive-by reading
4.Long-range RF
5.PLC (Power Line Carrier)
6.Inductive pad reading
 

RODALCO

Well-Known Member
Phasor
In New Zealand we have a similar set up for larger customers, or ones with difficult access and who are on the time of use TOU tariffs.
These meters have a landline or cellphone connection and dial out by themselves or are read via dial up through the main meter reading computersystem.

These systems have been in use for at least 10 years by now.

I used to install these GEC, PPM meters and fit cellphones for the comms from mid 1990's till about 2001, before transferring to the technical services and maintaining the HV and LV distribution system in Auckland.
 
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