TCC CSD 909 PRM Communication Security Device
© Brooke Clarke 2013
Technical Communications Corp TTC) (home page) makes a number of encryption devices for voice and data communications. Patent 3610828
Privacy communication system talks about the simple and analog voice systems that use time and/or frequency shifting (easy to break) and the complex systems that do the encryption in the digital domain (expensive).They then describe a new type of system where they use digital pseudorandom signals to modify the audio signal thus achieving a more secure system at lower cost.
This Communications Security Device is intended for use with either voice or data by selecting which one using a front panel switch. It does not have a FILL port, but instead uses 5 thumbwheel switches to set a code that must be set the same on all devices in a network.
There is no provision for a battery either as main power or as keep alive. The primary power comes through the 14 socket connector that's the same as the POWER connector used on the PRC-25, PRC-77 radios and you can use the Power Connector Kit to make a cable for it.
Radio Connector
The front panel connector has 14 sockets.
CSD909
RADIO
Pin
CSD909
Nomen
CSD909
Function
RT100
Handset
Connector
RT100
Function
A
GND
Ground
(chassis gnd)
ground
B
SHI
Headphone Hi In
3 Vpp 500 Ohms
Headphone out
C
PTT
Push To Talk
PTT
D
MHO
Mike Hi Out
15 mVpp 200 Ohms
Mike In
E
+12VDC
Power to CSD909
F
?
H
?
J
?
K
MLO
Mike Low Out
A
L
SLI
Headphone Low In
A
M
Key Erase
normally gnd
N
?
P
?
R
?
Shell
ground
Fig 1 5 digit code wheels and variable caps for Rx In, Tx out, Rx out
Fig 2
Top board has analog circuitry.
2nd board down has micro processor or controller
3rd board down has thumbwheel switches & 4 MHz oscillator for uP/uC, Red pushbutton switch S9
bottom board has many ICs (maybe digital or analog).
3610828
Privacy communication system, (TCC), Oct 5, 1971, 380/260, 380/274, 380/275 - a pseudorandom phase, either 0 or 180 deg, is modulated on the audio.
3691414
3723878 Voice privacy device, (TCC), Mar 27, 1973, 380/39, 380/44, 380/275 - classical invert then code word phase modulation
4195202
Voice privacy system with amplitude masking, (TCC), Mar 25, 1980, 380/39, 380/35 -
"A simple illustration is a number count of one to ten. Under most conditions, a listener, by analyzing the cadence of a scrambled signal, can determine that a series of numbers is being counted, even though the frequency content of the signal has been severely disturbed."4276652
Secure communication system with improved frequency-hopping arrangement, (TTC), Jun 30, 1981, 380/34, 380/38 - stepped LO inversion
4392021
Secure facsimile transmission system using time-delay modulation, (TCC), Jul 5, 1983, 380/243, 380/218, 380/216, 380/35 - ditigitizing FM modulated fax then using PR time delay
4433211 Privacy communication system employing time/frequency transformation, (TTC), Feb 21, 1984, 380/36, 380/269, 380/276, 380/28 -
Cryptography
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page created 8 Nov 2013.
