Parallel phone detection circuit
First Claim
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1. A line current detection circuit for use in a telephone set comprising:
- means for deriving a comparison current from the line current of a telephone line;
generating means for producing sequentially different values of reference currents;
means for determining when the value of a reference current generated by the generating means corresponds to the value of the comparison current;
means for storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and
means for subsequently comparing said stored reference current or a current based thereon with said comparison current and for producing an output signal for controlling disconnection of the telephone set to the telephone line in response thereto.
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Abstract
A parallel phone detection circuit is described, the function of which is to enable a phone call to be transferred from a first telephone set to a second telephone set. The detection circuit maintains the first telephone set connected to the telephone line until the handset of the second telephone set has been taken off-hook, and then disconnects the first telephone set. The circuit operates by detecting the line current from the telephone line and produces the reference value for comparison purposes related to that line current.
24 Citations
17 Claims
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1. A line current detection circuit for use in a telephone set comprising:
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means for deriving a comparison current from the line current of a telephone line; generating means for producing sequentially different values of reference currents; means for determining when the value of a reference current generated by the generating means corresponds to the value of the comparison current; means for storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and means for subsequently comparing said stored reference current or a current based thereon with said comparison current and for producing an output signal for controlling disconnection of the telephone set to the telephone line in response thereto. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of detecting a telephone line current comprising the steps of:
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deriving a comparison current from the line current of the telephone line; producing sequentially different values of reference current; determining when the value of a reference current corresponds to the value of the comparison current; storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and comparing said stored reference current or a current based thereon with said comparison current and controlling disconnection of a telephone set to a telephone line in response thereto. - View Dependent Claims (14, 15, 16, 17)
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Specification