How to automatically answer phone and emit dial tone?

Discussion in 'General Electronics Chat' started by drvan, Apr 23, 2012.

  1. drvan

    Thread Starter New Member

    Apr 23, 2012
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    The short of it: I'm looking for a device to automatically answer a ringing phone and emit a dial tone. Does anyone know of a commercial device that can do this for under $100?

    Long story: I'm home for the summer months from school and staying at my mom's place. Recently, her building has issued key fobs to replace the traditional keys that open the downstairs lobby door and my old key doesn't work. Building management won't give her another key fob unless she writes me into the lease, in which case her rent will go up and it's a huge pain in the butt, etc.

    There is a buzz system which connects to a dedicated phone line in each tenants apartment, so I usually call up, mom answers, and hits #6 to let me in. I have a key to the apartment which is fine, but the problem arises when she's not home and can't let me into the lobby.

    So, I'm looking for something on the other end can answer and hit #6 to let me in. Alternatively, having the downstairs buzz call forwarded to my cell phone would also work but I doubt there's anything out there that would accommodate this.

    I've toyed with an electronic answering machine, trying to record the #6 dial tone as the message, with the idea that the call automatically goes to the machine and the tone is heard, but it didn't work. I'm thinking either the tone was too faint or the #6 key must be pressed physically - I'm not sure. I might try again if I can find a tape-recorder style answering machine to make a louder recording.

    So.. any ideas or suggestions? Or if this is posted in the wrong area, maybe a nudge in the right direction. Thanks! :)
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,429
    3,360
    What you need is something that controls an answering machine.
    You can call your own phone/answering machine, when it answers you enter a private code.
    From there you can control the answering machine remotely.
    Get the answer machine to send the #6 dual tone to open the door.
     
  3. BillO

    Well-Known Member

    Nov 24, 2008
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    136
    You could also use a small microcontroller and a DTMF generator, like the HT9200 to answer the phone and produce the required tones. You'd need a few additional parts, like an op-amp, a relay, a signal transformer, etc.., but you could make something quite slick.
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,227
    So pushing #6 on the phone you are calling from after the answer machine picks up doesn't work?

    What is this "dedicated phone line". Is it a separate wire?
     
  5. BillO

    Well-Known Member

    Nov 24, 2008
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    Wouldn't be very secure if it did.
     
  6. drvan

    Thread Starter New Member

    Apr 23, 2012
    3
    0
    BillO, sounds promising. I don't know the first thing about circuitry, so I figure I'll have to read up quite a bit on this site.

    Crutschow, the phone I am dialing from isn't really a phone - it's the buzzer dial pad in the lobby. I guess it's not really a dedicated phone line, but since we don't have an outgoing landline (we both use cell phones) the phone jack in the wall is dedicated to the buzzer downstairs.

    I haven't tried pushing #6 from downstairs when the call is picked up. It does seem to defeat the purpose of security but I'll give it a try nonetheless.
     
  7. drvan

    Thread Starter New Member

    Apr 23, 2012
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    0
    BillO, do you think playing a recorded DTMF tone will work, or is using a DTMF generator necessary?
     
  8. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,227
    That's true about security.

    So the answering machine is connected to the dedicated line from the lobby. I wonder how the lobby door differentiates a #6 lobby signal from a #6 room signal? :confused:
     
  9. P-MONKE

    Member

    Mar 14, 2012
    83
    5
    I think you need to think this through very carefully. What you are attempting to do, in essence, is modify/circumnavigate the buildings security system.
    You may find that in the unfortunate event of a break-in that the buildings/personal insurance lawyers will claim that you've invalidated the terms of that insurance and this could end up costing you and your mother much more than if you were put on the lease in the first place.

    Come to think about it, your mother's insurance would probably be invalidated by you staying there with out being on the lease anyway, regardless of the changes to the security system.

    Sorry to be so negative. It's sad, but probably true: Insurers will more than happily take your money, but will use every loophole available to them to avoid paying out.
     
  10. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Every time a salesman or intruder buzzes the apartment to sell windows and doors or "duck" cleaning, your Mickey Mouse idea will answer the telephone and dial #6 to let the salesman or intruder into the building.
    Your idea needs some brains to determine friend or foe.
     
  11. BillO

    Well-Known Member

    Nov 24, 2008
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    136
    It should work if it was a good recording.

    But please don't ignore the security aspects of this. You will basically be circumventing the security that the building put in place. This was prbably both an insurance and municipal requirement. Your circumvention will almost definitely leave you open to legal action if it is discovered and probably a jail sentence if someone gets in there and commits a crime.

    If you proceed with this, and I don;t think yo should, you will have to use extreme caution and put some real intelligence behind the interaction so that there is some sort of obfuscated protocol involved, not just simply answer the phone and dial 6.

    I advise you to re-consider and not go ahead with it.
     
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