Written by: Mavicon M.D.
Design: The Ear and Mavicon M.D.
Diverter Plans
Parts List:
Everything can be obtained at your local Radio-Shack. As much as
i hate that store, they are convenient...
RLY1 DPDT relay
T1 1:1 audio transformer
D1 1N914 or similar diode
D2 large LED
LMP1 neon lamp
R1 10 k
R2 photocell
R3 22 k
R4 47 k
Q1 2N2222, 2N3904, 2N4401, most any other NPN switching
transistor
1 nine volt battery. The negative terminal goes to ground on the
schematic. Positive terminal to +9 volts.
Black electrical tape
Assembly:
The best way to assemble the design is to grab one of those small
copper lined perfboards from Radio-Shack. They are nice to work
on, and can easily be trimmed down to a minimum size once
everything is soldered in. The process is the same as any other,
solder all the parts in per the schematic. The photocell must be
in a position so that the light from the neon lamp(LMP1) and the
LED(D2) both shine on it. No other light must get in, so use
some black electrical tape to seal it all up. All the polarity
must be observed. Whichever direction you put the LED in, you
must remember (color code your wires, green is positive, red is
negative, yellow is positive, black is negative) the negative
side of the line must go to its negative side. The same goes for
the transformer. The positive side of each line has to be
connected to the correct pair on the transformer. On the Radio-
Shack transformers, put positive of both lines on the Red and
Black pairs, The negative on Yellow and White. Our prototypes
have reached less that 1" x 1" in size.
Theory of Operation:
The diverter works on some basic electronic principals.
Step by step:
The phone rings. The neon lamp is activated by the high
voltage(88 p-p) ac and flashes. This light shines on the
photocell, decreasing its resistance. When this happens, the
positive voltage flowing through the photocell and the 10k
resistor exceed the breakdown voltage of the base of the
transistor and switches that transistor on. Once the transistor
is on, current flows freely from emitter to collector, energizing
the relay. The relay's two sets of switches connect both lines
to the 1:1 audio transformer, effectively taking both lines off
the hook and coupling any audio signals from either line to the
other one. Once this happens, current is now flowing through the
transformer, relay, and LED loop. This current lights the LED
and that light shines on the photocell. This is what keeps the
device latched. The light from the LED keeps the photocell
resistance low enough to keep the transistor on. Now, you make
your call and get on with your business. You hang up. Now, the
local CO keeps current flowing through the indial line for about
5 seconds, at which point it drops down for a second or so and
then goes back up. This is the signal the device uses to
determine when you've hung up. When the current drops down,
there is no light from the LED, and the photocell resistance
raises enough to turn the transistor off and delatch the entire
system.
Applications:
The applications are relatively obvious. Hook it up to two
unused lines and make free calls. Hook it up to two payphones,
and red box calls. The only thing to watch out for is ringing.
If you hook it up to a residential line for the indial a small
(maybe 1/8) of a ring occurs when you call, tipping off people
inside the house.
|-------------------------------------
| | o +9V
| L1+ T1 | |
| o-------wwwww----------| | |
| | | |
| L1- | | |
| o-------------| | | o--------|
| | | | | |
| | | | | |
| | | | | |
| L2- | |---l----------l---------l--| _____
o-------\ LMP1 | | | \| | | w | /^\ D1
R4 47k * | | | | |\ | w | /---\
--\/\/--/ | | | | | | | w | |
| | |-l----------l-----------l--| |
| | | RY1 | | |
o L2+ |------| | | |
| | o---------
| | |
| | ----|
| D2 | /
| |\ | T1 | /
|----------| >|-----wwwwww---------- /
|/ | 000
|--------- 000 Q1
| 000
oooo | \
o o 10k | \
o-------o-/\/\/o------------/\/\/---| \
+9V o o R2 \ R1 |
oooo / 22k -----
\ R3 ---
| -
|
-----
---
-
_/_/_/ _/ _/
_/ _/ _/_/_/ _/ _/_/ _/_/ _/_/_/ _/ _/
_/_/_/ _/ _/ _/_/ _/_/_/_/ _/ _/ _/_/
_/ _/ _/ _/ _/ _/ _/ _/ _/ in
_/ _/ _/ _/ _/_/_/ _/_/_/ _/ _/ peace...