Cryptography – Communication system using cryptography – Circuit switched network
Reexamination Certificate
1966-02-28
2001-02-20
Gregory, Bernarr E. (Department: 3662)
Cryptography
Communication system using cryptography
Circuit switched network
C380S052000, C380S059000
Reexamination Certificate
active
06192128
ABSTRACT:
The present invention relates generally to improvements in telephone line disconnects and the like, and more particularly to new and improved current-sensitive telephone-line disconnects wherein the disconnect operates to close the telephone lines by means of the telephone line current during a call, and wherein the disconnect automatically operates to break all telephone connections between the incoming lines and the telephone when the handset is cradled and the line current drops to zero, so as to prevent the use of the cradled telephone for clandestine listening techniques.
In the field of telephone-line disconnects it has been the general practice to employ mechanical-type disconnects, such as a plug and jack, to break all telephone connections. Although such devices have served the purpose they have not proved entirely satisfactory under all conditions of service for the reasons that they rely on the user and require him to manually connect the lines prior to each phone call and then to disconnect all lines after each call is completed. This necessity for manual disconnection of the telephone lines is particularly bothersome and time-consuming when the telephone includes a plurality of lines for auxiliary purposes in addition to the voice lines, and where a large number of plugs and jacks are involved.
The general purpose of this invention is to provide a telephone-line disconnect which embraces all of the advantages of similarly employed devices and which possesses none of the aforedescribed advantages. The present invention provides automatic protection against the use of cradled telephones as clandestine listening devices by protecting against such techniques as radio-frequency saturation, audio pickup and hidden transmitters which use the telephone set as a source of power. Several embodiments of single and multi-line disconnects are included in this invention in order to meet various operational requirements such as, for example, variations in available telephone line currents in different countries.
Each embodiment of this invention uses the same basic principles of operation and provides the best possible semi-automatic or automatic isolation between the cradled telephone and all outside wiring by using circuit-breaking devices, such as relay contacts, to break the connections. When the telephone is not in operation, open relay contacts automatically and completely disconnect the telephone from all incoming lines. Means are provided to operate the relays and close the contacts when the telephone is to be used. Upon completion of a call, the handset is cradled and the line current drops to zero which automatically disconnects all wiring to the telephone, thus precluding the necessity of the user disconnecting the multiplicity of lines after each call. In this way the successful operation of the disconnect is not dependent upon the user and is not subject to compromise by personnel error, are mechanical disconnects.
An object of the present invention is the provision of a telephone-line disconnect system which will protect against the use of cradled telephones as cladestine listening devices.
Another object is to provide a telephone-line disconnect system which will provide protection against such listening techniques as radio-frequency saturation, audio pickup and the use of hidden transmitters which use the cradled telephone as a source of power.
A further object of the invention is the provision of the above-mentioned disconnect system wherein the telephone line current is used to control the opening or closing of all the telephone lines.
Still another object is to provide a telephone-line disconnect system which automatically disconnects all telephone lines when the telephone is cradled and is not in use.
Yet another object of the present invention is the provision of the above-mentioned disconnect system which will be capable of operation for a wide range of telephone line currents.
A still further object of this invention is to provide a telephone disconnect system which is not solely dependent on the user for its operation and which is not subject to compromise because of personnel error.
With these and other objects in view, as will hereinafter more fully appear, and which will be more particularly pointed out in the appended claims, reference is now made to the following description taken in connection with the accompanying drawings in which:
REFERENCES:
patent: 3123672 (1964-03-01), Ross
Myers Edwin C.
Rauen Theodore J.
Edelberg Barry A.
Gregory Bernarr E.
Stockstill Charles J.
The United States of America as represented by the Secretary of
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