THE MAGENTA BOX
                               ---------------

    This is a portable ringing generator which, if connected to a phone
    line, will make the phone on the end of it ring. It works by using a
    relay as a vibrator to generate A.C. which is then stepped up by a
    transformer and fed through a capacitor into the phone line to make the
    phone ring!

    YOU WILL NEED:

    One 5V relay with single pole change-over (SPCO) contacts
    One 6-0-6V mains transformer {KEZ SEZ: US users see text for mod.}
    Two 2uF 250V non-electrolytic capacitors
    One 6V lantern battery
    One push-to-make switch
    Wire

    HOW TO MAKE IT:

    The circuit diagram shows the relay in the normal state, ie when
    current is NOT Flowing!

           ---- SWITCH
       +---o  o-------+----------------+    +----------------+
       |              |.               |    |                |
    -------            }             6 |.  .|                |
      ---        RELAY }                }  {                  
    -------      COIL  }              0 }  {               OUTPUT
      ---              }           +----}  {             TO PHONE
    -------           |'           |    }  {               WIRES
      ---        COM  o NC         |    }  {    2*2uF 250V   
    -------   +-----o/             |   |'  `|                |
      ---     |       o NO         | 6 NOT  |   +---||---+   |
       |      |       |            |  USED  |   |        |   |
       +------+       +------------+        +---+---||---+---+
                                                       

    HOW TO USE IT:

    Connect the output wires to a suitable beige boxing point on a phone
    line. {or use a modular plug - middle two pins of the US type, outer
    two pins of the four-way UK type}

    HOW IT WORKS:

    The telephone ringing voltage is about 90V rms, which is about 255V
    peak to peak. This circuit feeds 6V peak to peak into the 6V winding of
    a transformer, which should generate 240V peak to peak in the 240V
    primary. {So in America you will have to use a 3-0-3V transformer to
    get the right step-up ratio, as your mains voltage is only 120V.} The
    relay is wired through its own contacts. At first a current flows, so
    the contacts change over and the battery current now flows into the
    transformer instead of the relay coil. This produces a pulse of current
    in the other winding, which flows through the capacitors and into the
    phone line. Meanwhile, the relay isn't connected any more and so flies
    back. This produces a pulse of current in the opposite direction on the
    mains side of the transformer. Any phone on the line will ring while
    the switch is held closed. With practice you should be able to emulate
    the ringing sound perfectly! It will certainly confuse a few people!


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    disclaimer: this is for informational purposes only. no responsibility
    is accepted for any consequences of use or misuse of any information
    contained herein. any material whose source i have not acknowledged is
    believed to be my own - if it sounds like something you invented, just
    remember great minds think alike.