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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 des-
cribed 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 direc-
tion.  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

