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External bell

Discussion in 'General Electronics Discussion' started by Al., Jun 12, 2014.

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  1. Al.


    Jun 12, 2014
    Hi there, I'm a bit stuck. I'm looking for an external bell to run off an optipoint 500 digital phone. There is an "acoustic adapter" that plugs into the back, and the bumph in the manual says the following:

    2. Second contact (PIN 4 and 5)
    This provides the ring input status.
    This contact can provide an external signaling mechanism when the telephone rings. This
    is important when connecting a secondary bell or similar device. Once again, observe the
    electrical connection values for this connector as well (24 V - 60 V, 5 W; do not connect an
    inductive load without surge protection). However, you can also connect a relay instead of
    the lamp, with this relay then controlling the 220 V secondary bell

    Contact Load
    Both contacts can carry the following load:
    5 W with 24 V a.c. or 60 V d.c.

    My question is, am I looking for a ready made unit, or am I looking for a relay (I have a vague idea of what that is from my school days 30 odd years ago...) and a bell, or a kit or what.......

    Many thanks, Al.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    I wouldn't know what you're loooking for.
    There may be complete units to buy. Your manual should tell you the manufacturer's part number.
    You can also build a unit of your own. From the desccription I take it that you will need an external power supply (AC 24V or DC 60V) which will be switched by the phone's output. This voltage can be used to
    • drive a bell directly as long as the bell is rated for AC 24V or DC 60V and less then 5W
    • drive a relay wehre the relay's coil needs to be rated according to the voltage switched - in tis case only DC is suitable since relays for AC are difficult to come by. The relay can in turn drive any other signalling device (bell).
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    As Harald says. Also you need some kind of suppression on the load, to protect the relay contact in the phone. If you're switching an AC voltage directly onto an AC bell, you need an R-C suppressor. If you're switching a DC voltage onto a DC bell or the coil of a relay that controls the bell, you need to connect a diode (e.g. 1N4004) across the load (the bell or the relay coil) with its cathode to the side that has the positive voltage.
  4. shrtrnd


    Jan 15, 2010
    I don't know the systems available outside the U.S.
    I also don't know if this is for home use, or an industrial site.
    I wanted a remote annunciator and light for home use, so I'd know when the phone was ringing in one room, while I was on the other side of the house.
    There were plenty of hobby circuits available on-line, but I found plenty of commercial units available also while Googling. I went with a model I found on-line.
    If this is for an industrial site. I'd go commercial anyway, just to save labor from the plant electrical workers.
    Most of us on this site think first of how we'd do-it-yourself. But there are times when, unless you're a die-hard hobbyist who really wants to do and learn yourself;
    it's better to just buy the product somebody already created to do the job, rather than reinvent the wheel.
    Google what you want from a commercial vendor. That's my take on this.
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