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- 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!
-
-
- Brought to you by ...... . .... . . ... .....
- : :..: :.. :.' .:.......:.
- : : : :... : `. `... .:...
-
- 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.
-