Telephone isolation device
First Claim
1. An isolation circuit for connecting a user device to a communication line pair for full duplex communication on the line pair while providing an electrical isolation barrier between the user side and the line side of the isolation circuit, comprising:
- a pair of capacitors connected across said electrical isolation barrier, each of said capacitors having like first ends connected to said one side of said isolation circuit and like second ends connected to the other side of said isolation circuit; and
,means for transmitting an information signal across said capacitors from said one side to said other side, including means for differentially charging said like first ends of said pair of capacitors with said information signal, means for receiving said differential charge on said like second ends of said pair of capacitors, and means for converting said differential charge on said second end to a restored information signal.
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Accused Products
Abstract
An isolation circuit for a telephone line interface includes a pair of capacitors that differentially couple analog transmit and receive channels in full duplex communication across an isolation barrier. Each transmit or receive signal is processed to generate respective paired complementary signals. A switching network is clock driven to differentially charge the paired capacitors in incremental fashion with the paired complementary signals. On the opposite side of the barrier, a clock driven switching network receives the differential charges on the paired capacitors, generating paired complementary signals that are processed to form an analog information signal. Clock signals, off-hook and ringing signals are transmitted in similar fashion. The invention can use two pairs of capacitors that differentially couple analog transmit and receive channels in a user device across an isolation barrier to a line pair for full duplex communication. The interface circuit includes first and second oppositely directed capacitor isolation circuits. The first is disposed between the transmit channel and a hybrid circuit; the second is connected between the receive channel and the hybrid. The transmit capacitor isolation circuit has an input located on the user device side of the isolation barrier and an output on the line side of the barrier and generates analog signals corresponding to analog signals at its input. A receive capacitor isolation circuit has an input located on the line side of the barrier and an output on the user side of the barrier and generates analog signals corresponding to analog signals at its input.
130 Citations
20 Claims
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1. An isolation circuit for connecting a user device to a communication line pair for full duplex communication on the line pair while providing an electrical isolation barrier between the user side and the line side of the isolation circuit, comprising:
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a pair of capacitors connected across said electrical isolation barrier, each of said capacitors having like first ends connected to said one side of said isolation circuit and like second ends connected to the other side of said isolation circuit; and
,means for transmitting an information signal across said capacitors from said one side to said other side, including means for differentially charging said like first ends of said pair of capacitors with said information signal, means for receiving said differential charge on said like second ends of said pair of capacitors, and means for converting said differential charge on said second end to a restored information signal. - View Dependent Claims (2)
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3. A method for transmitting an information signal across an electrical isolation barrier between a telephone line pair and a user device, including the steps of:
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connecting a pair of capacitors across said isolation barrier; differentially charging said pair of capacitors with said information signal on one side of said isolation barrier; detecting the differential charge on said pair of capacitors on the other side of said isolation barrier; and
,converting the detected differential charges on said pair of capacitors into a received signal corresponding to said information signal. - View Dependent Claims (4)
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5. An isolation circuit for connecting a user device to a communication line pair for full duplex communication on the line pair while providing an electrical isolation barrier between the user side and the line side of the isolation circuit, including:
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a pair of capacitors connected across said electrical isolation barrier; and
,switching means for synchronously switching an information signal alternately to each of said pair of capacitors to differentially charge said capacitors and transmit said information signal across said isolation barrier, whereby common mode noise is eliminated by said switching means.
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6. An isolation circuit for connecting a user device to a communication line pair for full duplex communication on the line pair while providing an electrical isolation barrier between the user side and the line side of the isolation circuit, comprising:
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a first pair of capacitors connected across said electrical isolation barrier, each of said capacitors having like first ends connected to one side of said isolation circuit and like second ends connected to the other side of said isolation circuit; means for transmitting an information signal across said capacitors from said one side to said other side, including means for differentially charging said like first ends of said pair of capacitors with said information signal, means for receiving said differential charge on said like second ends of said pair of capacitors, and means for converting said differential charge on said second end to a restored information signal; said means for differentially charging including differential translator circuit means for receiving said information signal and generating paired complementary differential signals corresponding to said information signal; said means for differentially charging further including switched transmit network means for incrementally and alternately switching said paired complementary differential signals to said first ends of said pair of capacitors. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An isolation circuit for connecting a user device to a communication line pair for full duplex communication on the line pair while providing an electrical isolation barrier between the user side and the line side of the isolation circuit, comprising:
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a first pair of capacitors connected across said electrical isolation barrier, each of said capacitors having like first ends connected to one side of said isolation circuit and like second ends connected to the other side of said isolation circuit; means for transmitting an information signal across said capacitors from said one side to said other side, including means for differentially charging said like first ends of said pair of capacitors with said information signal, means for receiving said differential charge on said like second ends of said pair of capacitors, and means for converting said differential charge on said second end to a restored information signal; further including another pair of capacitors connected across said electrical isolation barrier, and means for transmitting an off-hook signal from said user side to said line side of said isolation barrier. - View Dependent Claims (19)
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20. A method for transmitting an information signal across an electrical isolation barrier between a telephone line pair and a user device, including the steps of:
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connecting a pair of capacitors across said isolation barrier; differentially charging said pair of capacitors with said information signal on one side of said isolation barrier; detecting the differential charge on said pair of capacitors on the other side of said isolation barrier; converting the detected differential charges on said pair of capacitors into a received signal corresponding to said information signal; converting said information signal to paired complementary differential signals to charge said capacitors; and incrementally and reversibly charging said pair of capacitors in reiterative fashion in synchronism with a constant clock signal.
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Specification