Digital access arrangement circuitry and method for connecting to phone lines having a DC holding circuit with switchable time constants
First Claim
1. A communication system, comprising:
- phone line side circuitry that may be coupled to phone lines;
powered side circuitry that may be coupled to the phone line side circuitry through an isolation barrier; and
a DC holding circuit within the phone line side circuitry, the DC holding circuit being switchable to operate in a plurality of DC holding circuit phases, the DC holding circuit having a first time constant in at least a first DC holding circuit phase and having a second time constant in at least a second DC holding circuit phase.
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Accused Products
Abstract
A digital direct access arrangement (DAA) circuitry may be used to terminate the telephone connections at the user'"'"'s end that provides a communication path for signals to and from the phone lines. Briefly described, the DAA provides a programmable means for the DC termination for a variety of international phone standards. The invention may also be utilized with means for transmitting and receiving a signal across a capacitive isolation barrier. More particularly, a DC holding circuit is provided that has switchable time constants. A first time constant may be utilized during a first operation phase immediately after off-hook conditions to allow for fast settling times. Then, a second operation phase is entered in which a second time constant may be utilized. During the second operation phase the DC holding circuit operates slower to create improved low frequency performance.
68 Citations
28 Claims
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1. A communication system, comprising:
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phone line side circuitry that may be coupled to phone lines;
powered side circuitry that may be coupled to the phone line side circuitry through an isolation barrier; and
a DC holding circuit within the phone line side circuitry, the DC holding circuit being switchable to operate in a plurality of DC holding circuit phases, the DC holding circuit having a first time constant in at least a first DC holding circuit phase and having a second time constant in at least a second DC holding circuit phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of providing a communication system that may be coupled to a phone line, comprising:
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coupling an isolation barrier between powered circuitry and phone line side circuitry;
operating a DC holding circuit in first and second off-hook phases;
utilizing a first DC holding circuit time constant during the first phase; and
utilizing a second DC holding circuit time constant during the second phase, wherein the first time constant provides faster settling of the DC holding circuit than the second time constant. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A DC holding circuit for a communication system that may be connected to phone lines, the DC holding circuit comprising:
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at least a first circuit within the DC holding circuit, the first circuit affecting the settling time of the DC holding circuit;
at least one switchable circuit, the switchable circuit having a first state for a first phase of operation of the DC holding circuit and a second state for a second phase of operation of the DC holding circuit, the at least one switchable circuit coupled to the first circuit; and
at least one switched element selectively connectable to the first circuit by the switchable circuit, a time constant of the DC holding circuit changing depending upon the state of the at least one switchable circuit. - View Dependent Claims (17, 18, 19, 20, 21)
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22. A method of providing a DC holding circuit, comprising:
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forming the DC holding circuit with internal circuitry internal to an integrated circuit and external circuitry external to the integrated circuit;
providing a programmable circuit for switching the DC holding circuit between at least a first and second phase of operation; and
configuring the DC holding circuit to allow for the DC holding circuit to operate faster during the first phase and slower during the second phase. - View Dependent Claims (23, 24)
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25. A method of operating a DAA circuit, comprising:
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providing a DC holding circuit;
utilizing a first time constant of the DC holding circuit during a first phase of operation of the DC holding circuit; and
utilizing a second time constant of the DC holding circuit during a second phase of operation of the DC holding circuit, settling times of the DC holding circuit being faster during the first phase than during the second. - View Dependent Claims (26, 27, 28)
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Specification