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One or more anti- eavesdropping devices may be required to perform one or more of tests as described below: Line voltage off-hook:- This test allows the operators to measure the line voltage while the telephone is off hook (in use condition). Certain devices attached to the telephone lines or in the instrument itself alter the normal voltage and thus may be detected. Line voltage on-hook:- This is similar to the off hook voltage measurement. Tone Sweep :- In this test the instrument sweeps an audio tone to activate any devices such as close by transmitter (harmonic bug) which may be on the line or in the telephone instrument itself. Audio Listen-in:- This allows the operator to determine if the hook switch inside the telephone has been compromised. The hook switch normally disconnects the telephone from outside line when the phone is put back on the cradle. Defeating the hook switch allows the eavesdropper to listen to the room conversation when the telephone is not in use. High Voltage Pulsing:- This allows the telephone instrument to be tested for hook switch defeat methods which utilized remote triggered voltage controlled devices to pass room conversations to the eavesdropper while the telephone is on-hook. |
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