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Thread: Better caller ID solution than two resistors

  1. #1
    Join Date
    Jan 2002
    Posts
    81

    Better caller ID solution than two resistors

    Adding two resistors to drop current enough where the tivo modem can't take the phone line off the hook is not the best idea. Here is a MUCH better solution:

    Use a 1uF (i'm using 2.2uF) 250V mylar capacitor. Connect it in series with the ring (red wire) or tip (green wire) line of the phone line. This will block the DC from flowing, so the tivo will NEVER take the line of the hook or even attempt to. The FSK caller ID tones and ringing signal will pass through the cap and caller ID will appear on the screen. This is a better solution that using resistors, because the resistors can attenuate the caller ID tones enough where the modem will miss. The reactance of the capacitor is low enough not to attenuate the caller ID tones, so the modem will never miss anything.

    You can easily use two phone jacks for this, or make a PCB, or something like that. I took a phone cord with a RJ-11 connector on it, connected the ring (red wire) to one lead of the cap, and connected the other lead of the cap to a RJ-11 jack (doesn't matter which pin of the connector it's connected to, ring or tip, because just AC signals are passing, so no concern for polarity). Then connect the tip (green wire) to the remaining pin on the RJ-11 jack. The cap is in series with either the ring or tip, whichever you choose, it doesn't matter, and blocks the DC but passes the AC.

    This is much more effective than using two resistors, because it never takes the line off the hook or draws any DC from the line, and causes no interfearance.

  2. #2
    Join Date
    Dec 2003
    Posts
    6
    You can use this program. One side is for the tivo and the other side runs on the computer. The tivo has to be networked and you have to have a caller id capable modem.


    Quote Originally Posted by emuman100
    Adding two resistors to drop current enough where the tivo modem can't take the phone line off the hook is not the best idea. Here is a MUCH better solution:

    Use a 1uF (i'm using 2.2uF) 250V mylar capacitor. Connect it in series with the ring (red wire) or tip (green wire) line of the phone line. This will block the DC from flowing, so the tivo will NEVER take the line of the hook or even attempt to. The FSK caller ID tones and ringing signal will pass through the cap and caller ID will appear on the screen. This is a better solution that using resistors, because the resistors can attenuate the caller ID tones enough where the modem will miss. The reactance of the capacitor is low enough not to attenuate the caller ID tones, so the modem will never miss anything.

    You can easily use two phone jacks for this, or make a PCB, or something like that. I took a phone cord with a RJ-11 connector on it, connected the ring (red wire) to one lead of the cap, and connected the other lead of the cap to a RJ-11 jack (doesn't matter which pin of the connector it's connected to, ring or tip, because just AC signals are passing, so no concern for polarity). Then connect the tip (green wire) to the remaining pin on the RJ-11 jack. The cap is in series with either the ring or tip, whichever you choose, it doesn't matter, and blocks the DC but passes the AC.

    This is much more effective than using two resistors, because it never takes the line off the hook or draws any DC from the line, and causes no interfearance.

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