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Message: <blockquote data-quote="wgdchathuranga_1" data-source="post: 8457031" data-attributes="member: 257568">How to build a black box?I found this tutorial quite a long time ago and I don't know if it still works. Nevertheless , it might be interresting to read, you might even learn something from it! I would have gladly given credit to it's author but won't since I have no idea who he is. So here is his tutorial that remained unchanged ( I hope!):A BLACK BOX is a device that is hooked up to your phone that fixes your phone so that when you get a call, the caller doesn't get charged for the call. This is good for calls up to 1/2 hour, after 1/2 hour the phone Co. gets suspicious, and then you can guess what happens.What this little beauty does is keep the line voltage from dropping to 10v when you answer your fone. The line is instead kept at 36v and it will make the fone think that it is still ringing while your talking. The reason for the 1/2 hour time limit is that thephone CO. thinks that something is wrong after 1/2 an hour of ringing.All parts are available at Radio Shack. Using the least possible parts and arangement, the cost is $0.98 !!!! And that is parts for two of them! Talk about a deal! If you want to splurge then you can get a small PC board, and a switch. There are twoschematics for this box, one is for most normal fones. The second one isfor fones that don't work with the first. It was made for use with a BellTrimline touch tone fone.** Schematic 1 for most fones **** LED ON: BOX ON **FROM >--------------------GREEN-> TOLINE >--! 1.8k LED !---RED--> FONE!--///--!>--!! !------>/<-------SPSTParts: 1 1.8k 1/2 watt resistor1 1.5v LED1 SPST switchYou may just have two wires which you connect together for the switch. ** Schematic 2 for all fones **** LED ON: BOX OFF **FROM >---------------GREEN-> TOLINE >------- ---RED--> FONE! LED !-->/<--!>--! !---///---1.8k�Parts: 1 2 watt resistor1 1.5v LED1 DPST switch Here is the PC board layout that I recommend using. It is neat and is very easy to hook up.Schematic #1 Schematic #2************** ***************** * * ------- ** --<LED>--- * * ! ! ** ! ! * * ! <SWITCH> ** RESISTOR ! * * ! ! ! ** ! ! * * ! ! / ** -------- ! * * ! ! ** ! ! * * ! <LED>! / ** --SWITCH-- * * ! ! ** ! ! * * ! ! / *L * ! ! * F L * ! ! ! * FI>RED- -RED>O I>RED- ---RED>ON>-----GREEN---->N N>-----GREEN------>NE * h * E E * * E************** ****************Once you have hooked up all the parts, you must figure out what set of wires go to the line and which go to the fone. This is because of the fact that LED's must be put in, in a certain direction. Depending on which way you put the LED is what controls what wires are for the line & fone.How to find out:Hook up the box in one direction using one set offor line and the other for fone.*NOTE* For Model I switch should be OFF.*NOTE* For Model ][ switch should be set to side connecting the led.Once you have hooked it up, then pick up the fone and see if the LED is on. If it is, the LED will be lit. If is doesn't light then switch the wires and try again. Once you know which are which then label them. *NOTE* - If neither directions worked then your�lable the switch in its current position as BOX ON.</blockquote>

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