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...