Name: Phone Shield


Compact Device Protecting Telephone Conversations from Unauthorised
Interception at Receiver Side on Analog Phone Lines
Functional Features




Phone Shield is designed to protect confidential
information transmitted through telephone channels
from unauthorized cross talk.
The main principle of this protection lies in adding to the
communication channel a strong speech-like noise,
which reliably masks the useful speech.
Phone Shield is unique, as it is used only on one
subscriber's side, for instance in the office.
The user who is transmitting the confidential information
may use any non-protected telephone including even
pay phones (street call boxes).




Phone Shield is a unique stand-alone device designed to
protect duplex analog voice channels (for example,
public telephones) from unauthorized listening.
Phone Shield provides with confidentiality of telephone
conversations transmitted through unprotected
communication channels without digitalizing of
It differs from the devices like scramblers as there is no
need to have the same equipment on the other side of
the call, since Phone Shield protects the call working on
one side.




The operation principle of Phone Shield is based on the
following. At first Phone Shield generates the noise and
transmits it to the communication channel. Then
completely removes that noise.
The main advantage of this device as compared to its
counterparts is that in other devices it is often impossible
to detect the source of noise signal.
The concealed speech signal could not be filtered even
with the help of another Phone Shield.

Protection integrity of telephone lines has
always been a focal point in security in offices
as well as in private homes. Phone Shield is
the device which solves this problem.

The device has two modes of operation: normal and
u In normal (unprotected) mode Phone Shield has no
influence on the work of the telephone apparatus. To
switch on the protective mode the user should press
ON on the front panel.
u After the protective mode is on, the user on the
other side can transmit confidential information,
which meaning that all conversation said during this
period will be heard only by the Phone Shield user.
u The connection in the protective mode is one-way
connection (the Phone Shield user can only listen, his
partner on the other side - only speak).
u To return to the duplex connection the user should
switch off by pressing ON the second time and then
the device will work in normal (unprotected) mode.

Technical Data


Noise signal swing: 8 V p-p
Generated noise cancelling: 55dB
Power supply:
- Alternating current - 90-240V
- Direct current - 110-240V
Power consumption: 20 W

Document Path: ["1138-speech-technology-center-brochure-phone.pdf"]


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