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  1.                             Telephone Scrambler
  2.  
  3.       Protect your confidential telephone calls against intrusion with
  4.                        this easy-to-build scrambler.
  5.  
  6. Scrambling is the most effective method for eliminating unwanted evesdropping
  7. on your confidential calls.  It should be considered if you have reason to
  8. believe that unauthorized persons are or could be listening in.  A system
  9. consisting of two compatible telephone scramblers will permit normal
  10. conversation between you and your intended listener, while making all speech
  11. unintelligible to anyone listening in at either end of the line.  Only persons
  12. with a compatible unscrambler will be able to understand what is being said.
  13.  
  14. (Fig.1)
  15. Complete telehpone security is obtained with a TVS250 at both ends of the
  16. phone line forming a duplex scrambler/descrambler system.
  17. [Headset]-[TVS250]-[Phone]-[Phoneline]-[Phone]-[TSV250]-[Headset]
  18.  
  19. Circuit Design
  20.  
  21. The COM9046 voice scrambler/descrambler IC contains a crystal oscillator that
  22. that controls system timing.  The onchip oscillator requires an external 3.58-
  23. MHz crystal that is commonly used in TV color-burst applications.  The chip
  24. also contains switched-capacitor filters, so input speech must be filtered by
  25. an anti-aliasing single-pole, low-pass filter before it is applied to the
  26. audio input.
  27.  
  28. Parts List
  29.  
  30. All resistors are 1/4-watt, 5%, unless otherwise noted
  31. R1 100,000 ohms, PC-mount potentiometer, screwdriver adjust
  32. R2 500,000 ohms, PC-mount potentiometer, screwdriver adjust
  33. R3,R4 10,000 ohms
  34. R5,R6 3900 ohms
  35. R8,R9 100,000 ohms
  36. R10-R13 1000 ohms
  37. R7,R14,R15 51,000 ohms
  38. R16-R18 2200 ohms
  39. R20 150,000 ohms
  40. R21 5100 ohms
  41. Capacitors
  42. C1,C2 15 pF, ceramic disc
  43. C3-C10 0.1 uF, metal film
  44. C11,C12 2200 pF, ceramic disc
  45. C13-C15 0.001 uF, ceramic disc
  46. C16 1uF, 35 volts tantalum
  47. C17,C18 10 uF, 16 volts, electrolytic polarized
  48. Semiconductors
  49. IC1 COM9046 voice-scrambling IC, (Standard Microsystems)
  50. IC2 MC34119, audio amplifier driver (Motorola or equiv.)
  51. IC3 LM358 dual operation amplifier, single supply
  52. IC3 78L05A, 5-volt regulator (Texas Inst. or equiv.)
  53. Q1 2N2222A, NPN transistor
  54. LED1 green light-emitting diode, T1, 5mm
  55. LED2 red light-emitting diode, T1, 5mm
  56. Other Components
  57. S1 SPST slide, PC-mount, side-actuated switch
  58. S2 SPST slide, PC-mount top-actuated switch
  59. S3-S6 STS2400 PC, 2P4T slide, PC-mount, top-actuated (Augat/Alcoswitch or
  60. equiv) switch
  61. J1,J2 telephone jack 4-4, Type 616, PC-mount
  62. JU1-JU4 two-post jumper, 3/32 inch-on-center with insulated shorting clips
  63. XTL1 crystal 3.579545 MHz, metal case (ITT 4183 or equiv.)
  64. B1 9volt transistor battery, alkaline, standard
  65. Miscellaneous
  66. TVS250 PC board, 5-inch length of telephone cord terminated with standard
  67. telephone plugs, 9-volt transistor battery clip-type holder (Keystone No. 79
  68. or equiv.) with two 2-56 screws and nuts, 9-volt transistor battery terminal
  69. snap with leads, four rubber or plastic PC board feet and solder.
  70. :Note:
  71. The following parts are available from Securicom, P.O. Box 5227, Chatsworth,
  72. CA 91313-5227 (818) 710-0110
  73. * COM9046 scrambler/descrambler IC only - $18
  74. * Double-sided, silk screened and drilled PC board - $20
  75. * A complete kit including PC board, all components, and 5 inch plug-
  76.   terminated phone cord - $59.95
  77. * Assembled and tested TVS250 with user's manual - $79.95
  78.  
  79. (Fig.2)
  80.               +5V
  81.                |                 |--|
  82.                o------|    |-----~--o---
  83.        2.2k R17~    R4~10k |     R2    |
  84.                o---<>-o----|--*+****   |  R11         R5
  85.                |   C3 |    |  *IC3a*---o--~---<>---o--~------o--(3)
  86.    MIC+-----0^0|      |    o--*-****          C4   |         |
  87.             JV4       |    |                       |      C11$
  88.                    R3 ~    |                  C5   |  R6     |
  89.    MIC------0^0-------|    |---~---<>--#    |-<>-o-|--~---o-----(2)
  90.             JV3       #       R21  C8       |    | |   C12$  |
  91.                                             |    | |      |--|    (Cont fig.3)
  92.                                             |    | |         |
  93.    Base audio Signal------------------------|    | |         #
  94.                                                R8~ ~R9
  95.    Base audio GND------------------------#       | |
  96.                                                  --o---------o--(1)
  97.                                                              |
  98.                                                              |
  99.                                                              |
  100.                                                              |
  101.                                                              |
  102.  
  103.  
  104. (Fig.2)
  105.           S1   ******
  106.       |---@----* IC4*---o--o--o-->+5v
  107.       |        ******   |  |  |
  108.       |          |      |  |  ~R13
  109.       =          |   C10<> <>C17
  110.       |B1        |      |  |  |
  111.       |          |      |  |  L LED Green
  112.       =----------0------o--o--|
  113.                  |
  114.                  #
  115.  
  116.  
  117. (Fig.3)
  118.  
  119.  
  120.     C1    XTAL          +5v
  121.   --<>--o-&-o---<>-     ^
  122.   |     |   |     |     |
  123.   #     o-~-o     # |---o
  124.         |R19|       |   |
  125.        *******      |   L LED2
  126.     3--*     *      |   ~ R10
  127.        *     *------|---o--S2----------------#
  128.     2--* IC1 *      |   |
  129.        *     *------|-| <>C6
  130.        *     *      | | #       R20       /JV1--
  131.        *     *      | |---------~-------Q1      Mic Input to Tele Base
  132.        *     *      |                     \JV2--
  133.        *     *------|---|
  134.        *     *      |   |
  135.        *     *      |   |
  136.        *     *--o---o   |
  137.  1--o--*     *  |   |   |
  138.     |  *******--|   |   |
  139.     |   |   |       |   |
  140.     |   o   o    R18~   ~R14      C14
  141.     |   |---|--<>---o   o---------<>---------------|
  142.     |   |   |  C18  |   |                   ^+5v   |
  143.     |   |   |       |   |   R15             |      |
  144.     |   |   o--<>---o   |---~-----o-----*******    |
  145.     |   |   |  C7   |             |     *IC3-b*    |
  146.     |   |   #       |          C13<>    *+    *----o
  147.     |   |           |             |     *     *    |
  148.     |   |-----------o             #     *     *    |
  149.     |---------------|      C9           *-    *    |
  150.                            <>----~---o--*******    |
  151.           -------~---------|     R12 |      |      |
  152.           |      R7                  |      #      |
  153.           |           C15  #         |-------------|
  154.           |        |--<>---|------|
  155.           |        |       |      |
  156.           |--------o---****|****  |                  Handset speaker
  157.                    |   *       *--|------------------>
  158.           ---------|---*  IC2  *  |
  159.           |        |   *       *  |                  Handset speaker
  160.           <>C16    |   *       *--o------------------>
  161.           |     |--|---*********  |
  162.           o-----|  |        R1    |
  163.           #        |----o---~-----|
  164.                         |   |
  165.                         |---|
  166.  
  167.  
  168. (~)=Resistor
  169. (<>)=Capacitor
  170. (@)=Simiconductor
  171.  
  172. I recomend that you call and purchase a better diagram for the TVS250 from the
  173. company listed above.  Remember, to make the scrambler work you must have two
  174. TVS250's, one on the callers phone and another on the receivers phone.  I
  175. haven't purchased a set yet, but this DOES work, information was gathered from
  176. radio electronics.  So, it is a reliable source, not just another dumb text
  177. file.  Good luck!
  178.  
  179. ->BB<-
  180.  
  181.