Telephone monitor circuit and method
First Claim
1. A communication system connected to a pair of telephone conductors which supply telephone service to a telephone subscriber, comprising:
- transformer means having a first winding connected to one of said pair of telephone conductors,a modem connected to a second winding of said transformer means, for communicating over said telephone via said transformer means,voltage sensor means for sensing the voltage across said telephone conductors and detecting a reduction in the voltage level across said conductors, such reduction indicating an off-hook condition of a susbscriber telephone unit, andswitch means, connected in series between said first winding and the other of said pair of telephone conductors, for connecting said transformer means to said pair of telephone conductors and for periodically disconnecting said transformer means from said telephone conductors during operation of said modem thereby permitting said voltage sensor means to check for an off-hook condition.
1 Assignment
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Accused Products
Abstract
A communication system is connected to a pair of telephone conductors which supply telephone service to a telephone subscriber. An optically coupled switch connects a first winding of a transformer across the telephone conductors. A second winding of the transformer is connected to a modem for communicating over the telephone conductors via the transformer. A voltage sensor circuit senses the voltage across the telephone conductors and detects a reduction in the voltage level across the conductors which indicates an off-hook condition of a telephone unit of the subscriber connected to the conductors. The voltage sensor circuit also detects the presence of a ring signal on the conductors. The switch is periodically opened so as to disconnect the transformer from the telephone conductors, and permit the voltage sensor circuit to check for an off-hook condition.
37 Citations
9 Claims
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1. A communication system connected to a pair of telephone conductors which supply telephone service to a telephone subscriber, comprising:
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transformer means having a first winding connected to one of said pair of telephone conductors, a modem connected to a second winding of said transformer means, for communicating over said telephone via said transformer means, voltage sensor means for sensing the voltage across said telephone conductors and detecting a reduction in the voltage level across said conductors, such reduction indicating an off-hook condition of a susbscriber telephone unit, and switch means, connected in series between said first winding and the other of said pair of telephone conductors, for connecting said transformer means to said pair of telephone conductors and for periodically disconnecting said transformer means from said telephone conductors during operation of said modem thereby permitting said voltage sensor means to check for an off-hook condition. - View Dependent Claims (2, 3, 4, 5)
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6. A method of sharing the use of telephone conductors which supply telephone service to the telephone units of a subscriber with a modem, comprising the steps of:
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connecting a first winding of a transformer across said conductors and connecting the second winding of the transformer to a modem, instituting communication over the telephone conductors via the modem, periodically disconnecting said first winding from at least one of said telephone conductors, during said communication, monitoring the voltage level across said conductors when said first winding is disconnected from said telephone conductors, and maintaining said first winding electrically disconnected from said telephone conductors when the voltage level across said telephone conductors is less than a predetermined level, whereby said modem does not interfere with operation of a telephone unit then in use. - View Dependent Claims (7, 8, 9)
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Specification