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Ringing Crosstalk triggers CID

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    Ringing Crosstalk triggers CID

    I recently setup a second phone line with a NetCID on each line. I have both lines on a 4 wire phone line from my KSU switch over to my HS computer. The distance is about 20 feet.

    When Line 1 rings all is fine. When line 2 rings then NetCID 2 returns the correct CID info but after 4 rings NetCID 1 returns a CID string with no number and "Unknown Caller"

    I have run tests that removed all other wireing issues except for the 20 ft of 4 conductor wire. So is it common for ring voltage to bleed over between wires - enough to trigger CID ?

    I plan on running a test with a run of Cat 5 tonight to see if that clears it up. Just wanted you guys opinions if the crossover signals make sense.
    Bruce

    "The universal answer is 42."

    #2
    The 90 VAC ringing signal could well couple between parallel wires, but not enough current to trigger the ringer in the affected line. The CID modem tones are only a volt or so, and I'd be surprised if this would couple at all. I suppose that harmonics of the ringer frequency (it's quite low) could fake the CID modem tone detector. Seems unlikely.

    You could test - take line 1 off hook and dial 1. Then call line 2 from your cell phone and listen to line 1's dead line and see what you hear at the CID time - between the 1st and 2nd ring. The flaw in this is that you are off-hook on line 1 which reduces the line impedance. So if you have a butt set (phone test set) use it in the monitor mode; an equivalent is a plain phone coupled to the phone line with a 0.1uF capacitor.

    Of course, physically isolating line 1 and 2 wiring is the acid test.
    Last edited by Stevech; December 1, 2004, 12:06 AM.

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      #3
      Well I moved both lines to a Cat 5 and still got CID triggered on both NetCIDs. So I left one line on the Cat 5 and put the 2nd line back to the 4 conductor wire. No more CID triggers on line 1 when line 2 rings.

      Thanks Stevech for the info. I knew it didn't make sense but it sure was happening.
      Bruce

      "The universal answer is 42."

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        #4
        hmmm. I'm surprised that the CID device is false triggered by the ringing current. Seems like the gibberish would somehow be detected as such and rejected by the CID device. Maybe newer/better CID devices don't do this - since lots of people have CID capable telephone sets and multiple lines.

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