It would be the service provider. The old AT&T "Truevoice" --ahem- "enhancement" had the effect of clipping modem transmissions of 2400 BPS or less. Had to do repeated battles with their engineers. They had an internal memo, the contents of which they were quite secretive of, but one engineer finally admitted to me it simply told them to turn off echo cancellation for the affected customer. From time to time some other engineer would turn it back on, thinking there had been a mistake, and more high level tech call fun ensued. I am under the impression they finally abandoned the "Truevoice" processing because of the general havoc it created with slower data transfers.
I don't KNOW that it was the case, but I wouldn't be surprised if credit card merchant transmissions were not being similarly affected.
Re: Comcast Telephone Service!!! The saga continues!!
Well I now have some more info to throw into the mix on this Digital Phone issue with Comcast that I will share. My hope is that it will help others as well.
It has been about 2 weeks since my last post on this subject. Since that time the customer has had continued daily problems with his phones as well as his high speed internet connection. He was ready to pull the plug on Comcast when they determined that there was a problem with an 'amplifier' in his area as well as a 'bad cable' underground and some connectors that was affecting some three other customers in his area.
Three days ago the equipment was changed and the cable replaced and all has been well since. Today I performed another test of the system to Central Station and OK. Did a DL and all OK.
The customer made the comment that most people at Comcast seem incompetent except for one the has made the above repairs and suggested that I call him since I did have some more questions.
I contacted the tech and he explained as above what he knew about the issues. I asked if he could tell me what the line voltages were so that I may re-activate the line monitor so as to be a little more comfortable with this Digital Voice technology. He indicated that he was not sure what the voltages were but would get one of his tech's on the line.
The tech said that (reading from the book) the following were the voltages.
ON Hook Voltage 24 - 48vdc OFF Hook Voltage 6 - 12vdc Ring Voltage 60 - 90vac
I explained about a concern with the ON Hook voltage potentially be as Low as 24vdc since the line monitor may see that as a problem on the line. He asked if I can adjust the threshold of the line monitor and I explained not any more possible than him boosting the output voltage of the modem.
I then asked if they had wired the panel properly for line seizure thru the RJ31X and he said that he did not know exactly. I put enough doubt in his head that he wanted me to talk to the 'Comcast Tech Trainer' that would know more about the details of what I was asking.
I had to explain that I will discuss with their Trainer but did not want to get into a long consultation in teaching Comcast how to connect an alarm panel for line seizure. He indicated that they have been installing this equipment from Philadelphia to Harrisburg for quite some time and didn't seem to have any problems with other alarms. I explained that maybe "others" were not looking as hard.
I am presently waiting for a phone call from the Trainer and will post the results of that conversation. Maybe Monday till I get a call back.
I already have an appointment next week to visit the site for a small upgrade and at that time will look at how they have put this together.
We hook alarm systems up to Comcast telephone lines here all the time. Comcast puts a protector "just like POTS" on the outside of the house that converts the signal to dialtone. We wire for line seizure there and all works fine. We also use Comcast for redundant phone lines at the CS, we have had no problem receiving any alarms with them.
I think a call to the alarm panel manufacturer would give more detail on the telco spec, but to me the off hook at 6VDC seems a little on the too light side for some TLM specs I have seen, especially if the line is bogged down with old gear with a high ringer equivalency.
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