I really like the quality answers that come out of this group. Thank you Dave. That is probably right on. But I am still to receive that confirmation from Bell Canada - Ontario Testing Center.
What is interesting is that I placed a call on the channel which is now suspected of being monitored by milliwatt toner and and when the channel was connected there was no milliwatt noise at all. So, the DMS switch they use or whatever monitoring tool they use along with it is an effective monitoring tool which is smart enough to turn off right before the channel connects. They probably test with different volume level on the 6 channels as part of standard monitoring procedure and read-out the output in 24 hours. So, with that aside, I should say that the PBX is in no way generating any milliwatt by itself and probably the Tx is being effected by the Rx toner....Too technical here so, I don't know. Volume is various on different channels with some having Rx and some having Tx or both.... What I would like to learn is that why is there even a need for Milliwatt tester? Does PRI use the same technology as any analogue phone call when it comes to the actual media? (I understand that same copper wire is used) I thought there was a modulation/demodulation of voice that happens and hence everything is truly digital and only testing tool needed would be to check for lost packets between the wall-mounted PRI box at customer site and the DMS switch in the CO. Having said that, I understand that tester is probably needed just to generate traffic over night. However, the varying degree in the frequency of the raw sound file which I recorded is now puzzling me. I thought the tester would prove 100% working or 100% not working. Now, that I think of it, it's probably the lost packets that creates that difference in frequency.....even noticeable by human ears. I have sent you the file I recorded from the Tx stream and converted it to a format that can play on VLC Media Player. They said that tech went and checked the lines and reconnected them. Problem is that the box on the street is shared by residential and commercial customers always and really the techs who work don't really care much about doing a proper job and it's easy to knock off or dilute one pair with another being installed. After all, for PRI it does look like any other copper pair. Maybe even not tagged or labeled at all. And I doubt too that any of the testing tool is left in the boxes on the street. They probably have a way of getting their information form the PRI box they install on customer site and turn on the milliwatt in the CO on the DMS switch. The guys in the CO never go outside and they really don't leave expensive equipment in the street boxes (specially not for 24 hours) Thanks again for the smart feedback. -Bruce > Date: Fri, 18 Feb 2011 09:59:57 -0500 > From: [email protected] > To: [email protected] > Subject: Re: [on-asterisk] Noise on PRI link that is hearable - Really?! What > does that mean technically? (Thought it's not possible) > > On Thu, Feb 17, 2011 at 11:44 PM, Bruce N <[email protected]> wrote: > > > Issue with a Bell PRI left me with few bad channels that I thought is never > > possible with a digital link like PRI. I thought that PRI channels are > > really created on the go and if there are no ALARMS then it means no noise > > level on any of the channels. I mean if there is something bad with the > > copper pair would that effect all the channels which are delivered over > > different frequencies? or does the noise effect one channel more that the > > other? So, I am very curious to know why I have Tx of 480 noise level > > (testing with ztmonitor) on channel 6 for example and Rx of 23 on channel 3. > > Channels 1-6 all have minor or major issues Rx/Tx noise level issues and the > > rest to 23 are fine as they show 0/0 in Rx and Tx. Notice all tests were > > done when no calls going on. > > > > > > So, I recorded the Rx and Tx streams and I see that the Tx stream on > > Channel 6 is giving me a continuous tone of 1001-1020 Hz. This is varying > > but mostly staying at 1001 Hz over 10 seconds of recording (tested with > > GString tuner of Android. Probably accurate to +/- 5 Hz). > > > > Bruce, > > You've piqued my curiosity. I agree that a 1000hz (or so) tone doesn't seem > like 'noise' or signal corruption. > > The frequency you identified is suspiciously close to a Milliwatt test at > 1004hz. Is there any chance that there's something weird in your dialplan > and you're generating that? Otherwise, maybe a test tech ordered a > Milliwatt test and it got left on from the CO side. If it's a new circuit, > maybe the install tech ordered the test and didn't cancel it. Having said > that, I thought that most milliwatt tests were dialed, not turned on from > the CO. > > I've had cases where work was ordered on one pair or circuit and because of > an error in communication between the repair tech and the switch tech, the > work was done on the wrong line. If it's not a new circuit, maybe someone > was working in the area and messed up your circuit while trying to fix > another. > > What's the level of the audio? Is it faint or is it at conversational > volume? > > Out of sheer curiosity, could you email me the WAV file you recorded? > > Dave
