What is the component in this schematic...?

Discussion in 'General Electronics Chat' started by mwalden824, Dec 29, 2011.

  1. mwalden824

    Thread Starter Member

    Mar 6, 2011
    51
    2
    Quick question. I have attached an image of part of a Caller ID schematic below. There is a component named Vs. What is it? Not even sure if it is a component, maybe just showing there is a voltage across Tip and Ring? I dunno. It looks like two diodes in opposite directions, but in the parts list below it says nothing. I have tried searching but not really sure what to search for. Maybe some sort of voltage regulation diode, zener? I haven't seen this particular symbol before.

    Thanks for any help,
    -Michael
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Looks like a surge protector.
     
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  3. mwalden824

    Thread Starter Member

    Mar 6, 2011
    51
    2
    Ok I think I found what it is. A DIAC. So I guess this is used for surge protection? So if the voltage exceeds its breakdown voltage, it will conduct, short circuiting keeping the voltage across Tip and Ring at or below its breakdown voltage, correct?

    If so, what rating DIAC should be used? Say one with a breakdown voltage of around 50 to 60 V DC, since there's around 47-50 Vdc on the Tip Ring Line? And atleast a 1 or 2 amp current peak output?

    I am building a Caller ID/Call Blocking Device with this circuit. This will be used for a VoIP (Vonage) line and not with a landline phone (like Bellsouth, or whoever offers them now).

    Thanks,
    -Michael

    edit: Now I just found a varistor has this symbol also. Which is probably more likely what this component is right? Again though, what ratings would be suggested for the application given above?
     
    Last edited: Dec 29, 2011
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It's a DIAC or a MOV or a TVS diode.

    The DC is usually around 45v-48v, but when the ringer activates, the line can get up to around 100v. If you used a DIAC, MOV or TVS that was rated for 120V to 130v, you'd probably be fine.
     
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