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         -= PHONE GADGETS =-

          Conference Caller
             Hold Button

                 by
       -- anonymous wizard --

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     >>>  Standard Disclaimer  <<<

	Anything you connect to the phone lines is *supposed* to be FCC
registered, to make sure it won't injure repairmen or damage
equipment.  The gadgets described in this file do NOT apply any extra
voltage to the line, and should be safe.  If in doubt, check with the
phone company before connecting any stuff to your line.  (These
gadgets do not put any extra "ringer equivalence" on your line,
either.)

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          CONFERENCE CALLER

	If you have two phone lines, you can this simple attachment to
set up your own conference calls.  You'll never pay to have an
operator set them up for you again.  Once you've called the two other
people on your two lines, you just throw the switch.  All three of
you can now talk to each other.

	Phone lines carry voices as audio frequencies superimposed on DC
control voltages (around 40-50 volts when not in use, with higher
pulses when ringing; around 10 volts when a phone is being used -- I
forget the exact numbers, but those are close.)

	The two lines can be connected through capacitors, so the audio
passes between the two, but the DC voltages don't interfere with each
other.  (If you simply short the lines together, the phone company
may not like it!)

Use this simple circuit:

             ! !    

 red --------! !---o: o------ red
             ! !    :
(line 1)            :      (line 2)
             ! !    

green--------! !---o  o------green
             ! !
              ^     ^
       capacitors  DPST
       .1 to 1 uf  switch
    (not critical)
(do *not* use polarized electrolytics!)

(This circuit is similar to the other conference caller mentioned on
the Roman Forum, which doesn't have the capacitors.)

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             HOLD BUTTON

	This gadget also is a variation on one posted on the Roman
Forum.

	Shorting the line is not a good idea.  A resistance of 1-2K is
enough to hold the line, without making the line look screwed up to
the phone company.


red ------o  o----\\\\------ green

          SPST    1-2K
         switch

(It doesn't matter which direction you connect this circuit in --
red-to-green and green-to-red both work.)

	If you like, you can add an LED that will light whenever you
have someone on hold.  Just connect the LED in series with the switch
and resistor (now about 500 ohms to 1.5k, depending on your LED --
experiment!).  Like this:

                           ^^
                          !\ !
red -----o  o----\\\\-----! >!--- green
                          !  !

       SPST sw. .5-1.5K    LED

	This circuit (with the LED) only works if it's connected in the
right direction.  Phone wiring isn't always done right; before you
wire this one in permanently, try switching the red and green wires,
and leave it in the direction that works.

                ENJOY!

X<>X<>X<  anonymous  wizard  >X<>X<>X
