Question by Shaun Skeels posted 19 Jan 2004
| ADSL Disconnections|
|I have a problem with my internal telephone line problem which affects my adsl modem? I have 5 extension sockets all hardwired internally and suffer from constant disconnection of the adsl service. If I have the modem plugged into the BT socket with all extensions disconnected; there are no disconnections of the service. I have also discovered that in the modem diagnostics program, under ADSL Tab; when connected only to the first point into the house, there are no 'loss of framing', 'loss of signal' or 'errored seconds' but with the other extensions connected, the ADSL diagnostic chart shows rising numbers in the loss of framing, signal and errored seconds whilst connected.|
Whilst having the extensions disconnected I have tested my extension cable with an insulation resistance tester and an ohm meter to check continuity of all pairs which all tested ok but I have found that the cable has what I think is an induced voltage of 12 volts measured to earth. I am now sure this is what is causing my adsl modem to disconnect.
The house extension sockets are wired in standard 3 pair cable and assume the induced voltage is being caused from mains electric cables within the house.
I wasn't to bothered about having all the points in the house but needed just one elsewhere so I decided to wire an extra point in CAT5 UTP data cable from my first point and clipped it well away from any mains cables through the loft and down the cavity in flexible conduit to the other point and connected it up.
Would you believe I still had the disconnections and the diagnostics of framing, signal and errored seconds were rising once again. I once again disconnected this cable and measured between each core and earth and had 12 volts again. I then wanted to prove that the induced voltage was from my house so I switched the main switch off at the distribution board and measured the cable again, 0 volts, switched it on again, 12 volts. I have tried isolating each circuit in turn but it doesn't go.
Does anybody know of anything I can do to solve this problem. Would having screened or foiled cable help? I don't want to spend money on expensive cable and find it still has this induced voltage. I thought that having CAT 5 cable being twisted pairs should give a balanced circuit and leaving them twisted right up to the connection.
Any help on what can be done or any information on EMI would be much appreciated.
Answer by Dmitri Abaimov posted 22 Jan 2004
It's just simply too much load on your phone line when you have all 5 telephones AND DSL modem connected at the same time. There is no simple solution to the problem because it is just so much current all the devices can draw from the central office switch cell.
I would suggest that, if you absolutely need all 5 phones operational at your location, take a look at some inexpensive small phone switches, KSU or PBX like AT&T Spirit or Partner. I guess, any refurbished unit would do, and you can get them real chip these days. Give eBay a shot, for example. Some changes should be made in the way your phone wires are laid out, too. They all will have to be home runs (separate cables) to the phone switch location.
I understand that this is not an easy solution, but, hey, in the old days they could have disconnected your service or even fined you if you connect too much load to their line! I guess, anything you can do to prevent that from happening will be better than having no service at all.
Dmitri Abaimov, RCDD
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