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Thread: Telephone distribution over CAT5e

  1. #1
    Automated Home Lurker
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    Default Telephone distribution over CAT5e

    Am trying to set-up distribution of my cable telephone line over CAT-5e structured wiring network. Currently I'm running the telephone line from my master socket, through a distribution box to my patch panel and then onto 4 remote locations.
    All 4 telephones are connected to the line, and ring.

    Only problem is that when I'm on the phone, I can hear my own voice amplified in the speaker of the receiver which is very annoying, and makes it difficult to hear the other end of the line. Does anyone know why this might be happening, and how I could resolve this?

    Many thanks..

  2. #2
    Automated Home Legend TimH's Avatar
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    Default Re: Telephone distribution over CAT5e

    Have you ruled out the phone itself as being the problem?
    Plug it into a phone socket directly (with ADSL filter if needed) and see if you get the same effect.

    If it's not the phone:
    * how have you connected to the master socket? plugged a phone cable into the front, or used the punchdown terminals inside the removable faceplate? (assuming it's an NTE5 socket)
    * do you get the echo if you plug the phone into the patch panel?
    * how are you connecting your phone to the extension wiring?
    * what type of cable are you using for the extension wiring?
    * what cores of the extension cable do you have connected?
    * do you get the echo on all four "extensions" or just on one or two?
    * are all the extensions the same length? (and how long are they?)
    * is the echo better/worse with different phones?

    Hopefully that should give you a few things to look at / try. Post back with the results and we'll take it from there :-)

    Cheers,

    Tim.

  3. #3

    Default Re: Telephone distribution over CAT5e

    Quote Originally Posted by Andy26
    Only problem is that when I'm on the phone, I can hear my own voice amplified in the speaker of the receiver which is very annoying, and makes it difficult to hear the other end of the line. Does anyone know why this might be happening, and how I could resolve this?
    Hi Andy,

    You *should* hear your own voice in the earpiece to a certain extent. It is called sidetone and is there to ensure you speak at the correct level. If there is no sidetone then you tend to shout into the phone, if there is too much then you speak quietly to avoid deafening yourself.

    Slight sidetrack here.... if you are trying to hear on the phone in a noisy environment, placing a hand over the mouthpiece is far more effective than covering the other ear because the sidetone will make the background noise audible along with the caller you are trying to hear. the human brain can filter sounds from different ears but not from the same ear so better to eliminage the noise from the call than block the other ear. If you can do both then so much the better

    Back on track.... Your problem seems to be excessive sidetone AND faint transmission. The usual cause for this is that there is a whacking great capacitor across the line shunting the low level audio signals.

    http://www.diyha.co.uk/telephones/pots.html shows the normal wiring for a phone socket to explain where the capacitor sits in the circuit. This is in the NTE5 so there should be no need for any other capacitors

    What type of RJ45 adapters are you using Master or Secondary ?

    Masters have a ringing capacitor in them.

    If you get the A & B reversed between two sockets you will end up putting two ringing capacitors in series across the line. This will severly attenuate the audio levels and give the symptoms you describe.

    Depending on the phones used there will also be a couple of other problems.

    When the BT sockets were first introduced, all phones needed three wires A, B and Bell. Many of the current phones on sale only actually need the A & B as they have internal ringing capacitors. It sounds as if your phones might be like this.

    Older phones that use 3 wires would effectively put the ringers or bells in series across the line because of the reversal and would give the following faults. With "bell" type phones, there would be a "ding" as you plugged the second phone in and the bell armature was permanently attracted to one of the poles. The current flowing through the bell coils would cause the line to be permanently busy. With phones that have an electronic "warble" they would just scream continuously and again put the line out of order.

    You dont seem to be suffering from either of those symptoms so I believe your phones are probably 2 wire but I do think you have mulitple capacitors and an AB reversal somewhere.

    HTH

    Keith
    KAT5.tv - affordable high quality AV Distribution
    http://www.kat5.tv

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