Telephone privacy device
First Claim
1. In combination with a telephone system of the type wherein there are one or more pairs of input lines,a plurality of telephones adapted to be connected to one or more such pairs of input lines, each telephone having a main control switch and a receiver assembly including a receiver electrically in series with said main control switch, said main control switch being closed when it is desired to talk, anda privacy device connected in series with said main control switch between the receiver of each telephone and any pair of input lines connected thereto, said privacy device comprising:
- voltage responsive means including an electronic switch in series with said receiver and effective upon closure of the main control switch of the telephone to which said voltage responsive means is connected and upon the presence of a voltage of at least a predetermined value across a pair of input lines to establish a relatively low impedance connection of the receiver of said telephone to said pair of input lines through said electronic switch, said voltage responsive means being effective to prevent the connection of said receiver to said pair of input lines when the voltage across the pair of input lines is below said predetermined value so that upon said voltage drop being so reduced the privacy device of any other telephone is effective to prevent the receiver of said other telephone from being connected to said pair of input lines;
manually operable means independent of said main control switch for increasing temporarily the impedance in series with said receiver so as to restore the voltage across said pair of input lines to at least said predetermined value to enable the privacy device of another of said telephones to connect the receiver of such other telephone to said pair of input lines; and
means for maintaining a circuit between said pair of input lines while said manually operable means is operated so that the current flow between said input lines is always maintained above a predetermined minimum value.
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Accused Products
Abstract
A privacy device for a telephone to prevent, unless desired, another telephone from being connected to the pair of incoming lines to which the telephone is connected. The privacy device employs voltage responsive means which is effective upon the telephone being connected to the incoming lines to establish a low impedance connection to the telephone only if the voltage across the incoming lines has initially at least a predetermined value. The low impedance connection drops the voltage across the incoming lines so that other telephones with the privacy device cannot be connected thereto. Means are provided for temporarily increasing the impedance across the lines to increase the voltage so that another telephone can be connected to the line when desired. This is done in a manner not to interrupt the connection between the lines but to maintain a minimum amount of current flowing therethrough so that the central office equipment does not detect an interruption in the line.
The privacy device is also equipped with means for turning it on regardless of the voltage across the lines when it is desired to use the telephone for intercommunication purposes within an office. When the intercommunication switch is pushed, the privacy device is caused to become conductive even though the value of the voltage across the lines is below the predetermined value.
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Citations
16 Claims
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1. In combination with a telephone system of the type wherein there are one or more pairs of input lines,
a plurality of telephones adapted to be connected to one or more such pairs of input lines, each telephone having a main control switch and a receiver assembly including a receiver electrically in series with said main control switch, said main control switch being closed when it is desired to talk, and a privacy device connected in series with said main control switch between the receiver of each telephone and any pair of input lines connected thereto, said privacy device comprising: -
voltage responsive means including an electronic switch in series with said receiver and effective upon closure of the main control switch of the telephone to which said voltage responsive means is connected and upon the presence of a voltage of at least a predetermined value across a pair of input lines to establish a relatively low impedance connection of the receiver of said telephone to said pair of input lines through said electronic switch, said voltage responsive means being effective to prevent the connection of said receiver to said pair of input lines when the voltage across the pair of input lines is below said predetermined value so that upon said voltage drop being so reduced the privacy device of any other telephone is effective to prevent the receiver of said other telephone from being connected to said pair of input lines; manually operable means independent of said main control switch for increasing temporarily the impedance in series with said receiver so as to restore the voltage across said pair of input lines to at least said predetermined value to enable the privacy device of another of said telephones to connect the receiver of such other telephone to said pair of input lines; and means for maintaining a circuit between said pair of input lines while said manually operable means is operated so that the current flow between said input lines is always maintained above a predetermined minimum value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In combination with a telephone system of the type wherein there is one pair of input lines and another pair of lines used for intercommunication purposes,
a plurality of telephones adapted to be connected to one or the other of such pairs of lines, each telephone having a main control switch, a first selector switch for connecting said telephone to said pair of input lines, an intercommunication switch for connecting said telephone to said pair of intercommunication lines, and a receiver assembly including a receiver electrically in series with said main control switch, said main control switch being closed when it is desired to talk, and a privacy device connected in series with said main control switch between the receiver of each telephone and any pair of lines connected thereto, said privacy device comprising: -
voltage responsive means including an electronic switch in series with said receiver and effective upon closure of the main control switch of the telephone to which said voltage responsive means is connected and upon the presence of a voltage of at least a predetermined value across the selected pair of lines to establish a relatively low impedance connection of the receiver of said telephone to said pair of lines through said electronic switch, said voltage responsive means being effective to prevent the connection of said receiver to said pair of lines when the voltage across the pair of lines is below said predetermined value so that upon said voltage drop being so reduced the privacy device of any other telephone is effective to prevent the receiver of said other telephone from being connected to said pair of lines; means independent of said main control switch for causing said electronic switch to become conductive to connect said receiver to the selected pair of lines even though the voltage across said pair of lines is below said predetermined value; and means controlled by said intercommunication switch for causing said last named means to be effective so that upon the user of any telephone actuating the intercommunication switch of that telephone and the main control switch thereof, the receiver of said phone is connected to said pair of intercommunication lines even though the voltage across said pair of lines is below said predetermined value.
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Specification