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.) * If you are a phreak, DON'T TELL THE PHONE COMPANY YOU WUSS!
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CONFERENCE CALLER
If you have two phone lines, you canthis 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.
