How to make a blackbox

This is for Deshi, welcome to the early-mid 90s, Original txt file from


What is a BLACK BOX? 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 Gestapo comes (you can guess what happens)

What this little beauty does is keep the line voltage from dropping to 10v when you answer your phone. The line is instead kept at 36v and it will make the phone think that it is still ringing while your talking. The reason for the 1/2 hour time limit is that the Gestapo thinks that something is wrong after 1/2 an hour of ringing. (I mean, come on)

(>Phone Modification Instructions<)

All parts are available Radio Shack. Using the least possible parts and arrangement, 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 board, and a switch.

                  **  Schematic 1 for most fones  **

                  **         LED ON: BOX ON       **

                FROM >--------------------GREEN->  TO
                LINE >--!   1.8k  LED  !---RED--> FONE
                        !              !

Parts:  1 1.8k 1/2 watt resistor
        1 1.5v LED
        1 SPST switch

*You may just have two wires which you connect together for the switch.

                   **  Schematic 2 for all fones  **
                   **        LED ON: BOX OFF      **
                 FROM >---------------GREEN->  TO
                 LINE >-------      ---RED--> FONE
                             !  LED !
                           !         !

Parts:  1 1.8k 1/2 watt resistor
        1 1.5v LED
        1 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 *  !      ! !  * F
               I>RED-      -RED>O I>RED-      ---RED>O
               N>-----GREEN---->N N>-----GREEN------>N
               E * 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. In order to find out, hook up the box in one direction using one set of wires for line and the other for phone.

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 switch was in the wrong position. Now label the switch in its current position as BOX ON.

(>Black Box Usage<)

The purpose of this box is not to people who call you so it would make sense that it can only be used to receive calls. When the box is ON then you may only receive calls. Your phone will ring like normal and the LED light on the box will flash. When you answer the fone the LED will light and the caller will not be charged. Hang up the fone after you are done like normal.


Nice post! Please fix the formatting tho’ :slight_smile:

1 Like

What’s up with the sketchy formatting @whatskrakan_01?

1 Like

The sketchy formatting is mainly because the file I got it from is from a site that no longer exists and didn’t have any sort of formatting. It has stuff that makes sense in English, like tabbing at the beginning of a paragraph, but looks horrible when you post it on a site with these kinds of formatting options. I’ll see what I can do to fix it.

1 Like

Heh, I’ve got the books to go with this. This post you got off of machacking looks like a rip from said manuals. Here’s what the schematics of those look like (The Second schem. & PC board are nonexistent in my copies though):

1 1.8K 1/2 Watt Resistor
1 1.5V LED
1 SPST Switch

(1) Open your phone by loosening the two screws on the bottom and
lifting the case off.
(2) There should be three wires: Red, Green, and Yellow. We'll be working
with the Red Wire.
(3) Connect the following in parallel:
     A. The Resistor and LED.
     B. The SPST Switch.
In other words, you should end up with this:
              (Red Wire)
(Line)-----!              !-----(Phone)
          /\/\/\ = Resistor
          O      = LED
          _/_    = SPST

(Note, this is from a .txt file)


This topic was automatically closed after 30 days. New replies are no longer allowed.