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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