Regards, Steve
Michael Welter wrote:
Just when I thought I couldn't be wrong, I was wrong. We have woodpeckers that drill into the arial telephone cables, and water seeps through the holes and partially grounds the tip and/or ring wires causing hum. I thought the hum/buz on my lines was a telco problem.
The Qwest HQ noise team assures me that my lines are within spec. Sure enough, when I listen on the test set the lines are clear.
The lines terminate at an Adtran 750 channel bank on my * system. When I reconnect the lines to the channel bank and make a call, I get the hum/buz noise. I have replaced every Adtran component (even the chassis), but the hum/buz stays with the lines.
From the CO we have a digital fibre optic system which terminates at a neighborhood cabinet. From there, analog copper cables distribute service to the houses. I'm suspecting that the digital-to-analog process doesn't give a smooth analog signal but rather a "stair-stepped" signal, with each step 1/8000 sec in duration (I wish I had a 'scope to confirm this.) The human ear can't hear this stair-stepped signal, so it's ok for POTS use.
However, when I put this stair-stepped signal to the channel bank, it converts it back into a digital signal. I'm thinking that, because it's not a smoothed signal, the analog-to-digital process injects hum and buz. Does _anyone_ have more information on this?
In the meantime I've had an ISDN circuit installed so as to have digital all the way to the * box. However, I can't get the ASUSCOM ISDNLink card to work with ISDN4Linux :-(
Cheers, Mike
P.S. The woodpeckers are still eating my house. There is a nest is an exterior wall which is driving my cats nuts!
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