Reconnecting telephone lines

[Andrew Gabriel]

Any line with ADSL through BT wholesale will connect to any ISP which hooks up to BT wholesale, IME. BT use the username to work out which ISP to route the session to - there's no hardwired connection to your ISP. The ISP might choose to reject it if it's not coming from the expected phone line, but I don't know of any which do this. I used to have AAISP on one line and BT business ADSL on another, and it didn't matter which line each modem was connected to - it was the login which decided which ISP you got, not which line you used.

[Dave Liquorice]

And the insulation is paper[*], dry paper is very thin and a good insulator wet paper isn't.

And blasted 'orrible sticky gunk it is too. Joints as in the wires are jelly filled though but not joints as in the box that covers the whole rats nest of pairs and beans. B-)

[*] My late father was the leading draughtsman at the Post Office Factory, Fordrough Lane until he retired about 30 years ago. So as I lad and youth I got to hear about cables and stuff.

[Andy Dingley]

I was an apprentice there for a few months, about the same time. Metal- bashing bench and machining course. Great fun.

They had a pair of shiny new PDP11/34s in the PCB CAD office, although most of the simpler work was still tape on mylar.

[Andrew Gabriel]

For these cables, it's more accurate to say air insulated, paper spaced.

[John Rumm]

It may not be hardwired, but I suspect there is more configuration than just inspecting the username. I had a customer who lost his BB a few months ago, and the fault turned out to be a problem at the BT exchange. He was getting sync, but was not being connected to plusnet even though the connection string was correct. They could not even see connection attempts in their radius logs. Plusnet had to get BT to rebuild the connection twice in the end to get normality restored.

(there were other odd factors at work on this one as well, since we could not even connect to the bt_test@startup_domain login either)

It may vary with exchange, however it does not seem to happen here. I have one line with plusnet, and another with idnet - both terminating at the same local(ish - 6km away) steam driven exchange. If I swap the modem leads over, neither service will connect until I also swap the login details over as well.

[Andrew Gabriel]

Might also depend on the service, e.g. 20CN or 21CN/WBC service. There was only one service (20CN) when I did this, so both lines would have been the same.

[John Rumm]

Possibly - or perhaps it makes a difference if you are talking to a large exchange with multiple DSLAMs, or a village one like ours. Pretty sure our exchange has not got 21CN (not even scheduled for an upgrade at the moment alas).

[Dave Liquorice]

Tape and mylar yes we had some "samples" when I developed an interest in electronics. Probably after my Dad's time at the factory, he never mentioned anything about CAD. Proper drawing boards, rulers, pencils and lots of helvetica letraset...

[Skipweasel]

My record for PCB artwork was 2000 holes on an A4-sized board. 6502- based self-contained numberplate printer.

[Andy Dingley]

Should have used a Z80, you'd have had it done with only 1000 holes

8-)

PCB fashion for prototyping at the moment is to CNC mill them, rather than etching. It makes hole drilling rather less tiresome too!

[Skipweasel]

Wasn't my design - I just translated the diagramme into glorious bicolour.

[<me9]

Did you havve to drill the board, It would have been a good test on drill bits.

[Skipweasel]

No - sent it to PCL, who appear to still be going nearly thirty years later.