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Is it possible, and safe to backfeed dialtone on a dry ADSL pair?

Started by dsk, December 21, 2013, 01:56:37 PM

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dsk

My parents in law has stopped using POTS, but they have their internet as before, ADSL.  If I  hook up an ATA (PAP2T) and feeds the line voltage back on the line  via a filter-box, and use another filter where the phone are connected, will it work? (or will the signal make problems in the other end of the system)  I could put in a pair of 120 nano-farad capacitors in the line to the exchange to keep that part of the line dry. (Same value as used in a filter)

Any experience with this, and what will the telco say?

dsk

unbeldi


twocvbloke

I wouldn't recommend altering the phoneline, if something goes wrong and the line ends up developing a fault due to your modifications, the phone co. could charge you (or your parents to be exact) for repairs and possibly even fine you for tampering with their hardware, it'd probably be much safer to install or reroute any extensions directly to the ATA, then the ATA to the modem/router, keeping the line and VoIP separate and the phone co. happy... :)

dsk

Quote from: unbeldi on December 21, 2013, 02:01:12 PM
Quote from: dsk on December 21, 2013, 01:56:37 PM
My parents in love has stopped using POTS, but they have their internet as before, ADSL.  If I  hook up an ATA (PAP2T) and feeds the line voltage back on the line  via a filter-box, and use another filter where the phone are connected, will it work? (or will the signal make problems in the other end of the system)  I could put in a pair of 120 nano-farad capacitors in the line to the exchange to keep that part of the line dry. (Same value as used in a filter)

Any experience with this, and what will the telco say?

dsk
Why don't you ask them?

They dont want me to use another phone company. :-)

dsk

dsk

 >:( They (my parents in law) did not want to try, they are finished with POTS!

dsk

AE_Collector

No second pair in the cable to run ADSL one one and phone line on the other?

Here "dry ADSL" still has talk battery via a CO line card on the line.

Terry


dsk

Since they were definite in their NO! I did not measure, but I have measured on another ADSL line from  Telenor earlier, and that was really dry, 0 volts! 
When opening the ADSL splitter it was the regular coils capacitor filter on the phone line side, and the modem had one 120 nano-farad capacitor on each wire.

I guess a lot knowledge has been lost during the last years, applying a dc voltage would help keeping the line free of noise. Traditionally the old 3 prong phone jacks used here had a resistor across the line (390 k ohms). This was abandoned sometimes in the later 1980'ies.

It was not commonly known why this resistor was in the jacks, we believed it was for measuring extra jacks (we had to pay a monthly fee for each jack) I'm pretty sure this kept a small sealing current preventing noise from bad splices. 

dsk

twocvbloke

I don't think ADSL needs the voltages that telephones do to operate, you have to think of it like a radio signal being fed from an aerial on the roof to the radio tuner, the only energy involved is what is broadcast and then received and sent to the tuner, so a "dry pair" may appear electrically dead to a multimeter, but to an ADSL modem, it's alive with signals ad a few millivolts... :)

As for resistors in sockets, our Master sockets have something like that too, I think it measures to about 0.5 REN, so to a linesman testing the pairs, the line appears connected even if there are no phones on the line (it's why with the GPO's "Plan 4" setup you needed a permanently wired bellset so the line wasn't left open-circuit)... :)

dsk

You are right, the voltage are not needed, but applying a little dc current may reduce noise caused by corrosion in bad splices. Should usually not be needed. Probably the reason by just having "dry" lines.  When dry is explained by no DC current applied.

dsk

AE_Collector

Here we always have line equipment on dry adsl lines but it may be so that the lines can be tested. We use 4Tel test equipment on all lines.

Terry