Current-sensitive telephone-line disconnect system
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsEdwin C. Myers, Theodore J. Rauen
Life of this patent
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Abstract
The circuit uses a current sensing device that is controlled by the telephone line current. The telephone lines are connected to the contacts of a push-button switch, and a diode bridge is connected across contacts of the switch. Further, the circuit has a DC slow-release relay that is located across the output of the diode bridge. The telephone lines are also connected to the relay contacts of the DC slow release relay. A capacitor is placed across the telephone lines, and another capacitor is placed between the diode bridge and one of the relay contacts of the DC slow-release relay. The two capacitors act to shunt any radio frequencies that occur in the circuit as a result of an attempt to obtain information by RF saturation techniques.
Claims14
A telephone disconnect system which operates to prevent the use of a cradled telephone as a clandestine listening device, comprising:
- a telephone network;
- electrical lines, series-connected with respect to said network and with respect to one another;
- a cradle switch operable to be closed so as to be series-connected with respect to said network and said lines;
- normally disabled current-sensing means maintaining said lines and said network in open circuit relationship;
- and
- switching means operable upon closure of said cradle switch to activate said current-sensing means and said network,
- thereby permitting electrical energy to flow through said electrical lines and said network.
A multiline telephone disconnect system which operates to prevent the use of a cradled telephone as a clandestine listening device, and which is capable of operating over a wide range of telephone line currents, comprising:
- a telephone network,
- a plurality of pairs of electrical lines selectively operatively coupled with respect to said network and wherein at least one of said pairs comprises voice transmission lines,
- a cradle switch operable to be closed so as to be series-connected with respect to said network and with respect to said voice-transmission lines,
- a normally disabled first current-sensing means maintaining said network and said voice-transmission lines in open circuit relationship.
- amplification means operatively coupled to said first current-sensing means, and
- switching means operable upon closure of said cradle switch to trigger said amplifciation means on by a transient,
- whereby said first current-sensing means, when energized and when said cradle switch is closed, operates to allow electrical energy to flow through said plurality of pairs of electrical lines, and
- whereby said first current-sensing means, when de-energized, operates to open said plurality of pairs of electrical lines.
Dependencies are inferred from the claim text.