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<> The BAD BOY'S (tm) and ABuSe <>
<> Presents 'How to Build a Telephone Scramber ' <>
<> By Bloodwing ->BB<- <>
<> Thx to Casual and Crusader <>
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Telephone Scrambler
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\Protect your confidential telephone calls against intrusion with/
\this easy-to-build scrambler. /
Scrambling is the most effective method for eliminating unwanted evesdropping
on your confidential calls. It should be considered if you have reason to
believe that unauthorized persons are or could be listening in. A system
consisting of two compatible telephone scramblers will permit normal
conversation between you and your intended listener, while making all speech
unintelligible to anyone listening in at either end of the line. Only persons
with a compatible unscrambler will be able to understand what is being said.
(Fig.1)
Complete telehpone security is obtained with a TVS250 at both ends of the
phone line forming a duplex scrambler/descrambler system.
[Headset]-[TVS250]-[Phone]-[Phoneline]-[Phone]-[TSV250]-[Headset]
:Circuit Design:
The COM9046 voice scrambler/descrambler IC contains a crystal oscillator that
that controls system timing. The onchip oscillator requires an external 3.58-
MHz crystal that is commonly used in TV color-burst applications. The chip
also contains switched-capacitor filters, so input speech must be filtered by
an anti-aliasing single-pole, low-pass filter before it is applied to the
audio input.
:Parts List:
All resistors are 1/4-watt, 5%, unless otherwise noted
R1 100,000 ohms, PC-mount potentiometer, screwdriver adjust
R2 500,000 ohms, PC-mount potentiometer, screwdriver adjust
R3,R4 10,000 ohms
R5,R6 3900 ohms
R8,R9 100,000 ohms
R10-R13 1000 ohms
R7,R14,R15 51,000 ohms
R16-R18 2200 ohms
R20 150,000 ohms
R21 5100 ohms
Capacitors
C1,C2 15 pF, ceramic disc
C3-C10 0.1 uF, metal film
C11,C12 2200 pF, ceramic disc
C13-C15 0.001 uF, ceramic disc
C16 1uF, 35 volts tantalum
C17,C18 10 uF, 16 volts, electrolytic polarized
Semiconductors
IC1 COM9046 voice-scrambling IC, (Standard Microsystems)
IC2 MC34119, audio amplifier driver (Motorola or equiv.)
IC3 LM358 dual operation amplifier, single supply
IC3 78L05A, 5-volt regulator (Texas Inst. or equiv.)
Q1 2N2222A, NPN transistor
LED1 green light-emitting diode, T1, 5mm
LED2 red light-emitting diode, T1, 5mm
Other Components
S1 SPST slide, PC-mount, side-actuated switch
S2 SPST slide, PC-mount top-actuated switch
S3-S6 STS2400 PC, 2P4T slide, PC-mount, top-actuated (Augat/Alcoswitch or
equiv) switch
J1,J2 telephone jack 4-4, Type 616, PC-mount
JU1-JU4 two-post jumper, 3/32 inch-on-center with insulated shorting clips
XTL1 crystal 3.579545 MHz, metal case (ITT 4183 or equiv.)
B1 9volt transistor battery, alkaline, standard
Miscellaneous
TVS250 PC board, 5-inch length of telephone cord terminated with standard
telephone plugs, 9-volt transistor battery clip-type holder (Keystone No. 79
or equiv.) with two 2-56 screws and nuts, 9-volt transistor battery terminal
snap with leads, four rubber or plastic PC board feet and solder.
:Note:
The following parts are available from Securicom, P.O. Box 5227, Chatsworth,
CA 91313-5227 (818) 710-0110