Modem with received signals and transmitted signals comprising signal sets
First Claim
1. Apparatus comprising:
- a first port for communicating digital signals and a second port for communicating bidirectional analog signals, anda modem coupled to the first port and the second port, includingreceive circuitry responsive to an analog signal received at the second port for converting said analog signal to a digital signal applied to said first port and for developing a maximum value N for said digital signal when said analog signal reaches a maximum analog level having a first magnitude, where N is an integer; and
transmit circuitry for applying an analog signal corresponding to a digital signal received at said first port and applied to the transmit circuitry, where the analog signal applied by said transmit circuitry to the second port has level of a second magnitude, where said second magnitude is at least twice as large as the first magnitude, and where the maximum magnitude of the analog signal developed by the transmit circuitry is developed in response to a value of N of the digital signal applied to the transmit circuitry, thus the analog signal received by said receive circuitry is characterized by a small dynamic range compared to the analog signal developed by the transmit circuitry, and the analog signal developed by said transmit circuitry is characterized by a large dynamic range compared to the analog signal received by the receive circuitry.
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Accused Products
Abstract
An approach for operating modems in synchronism with the A/D and D/A converters of the network limits the analog signals transmitted to the modem to low levels and concurrently restricts the received signals to large steps. This set of apparently conflicting signal limitations is achieved with a signal conversion process interposed in the communication path between the two hybrids. In one embodiment of this invention, the code conversion is implemented in an adjunct processor that is associated with a switch that participates in the communication path between the two modems. In operation, a call that needs the conversion process is identified by virtue of the calling party'"'"'s number and service associated service provision information. When it is established that both the calling party'"'"'s modem and the receiving party'"'"'s modem operate in the manner that requires signal conversion, conversion is executed. Echo cancellation may be applied to the signal in the code conversion apparatus to further improve performance.
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Citations
11 Claims
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1. Apparatus comprising:
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a first port for communicating digital signals and a second port for communicating bidirectional analog signals, and a modem coupled to the first port and the second port, including receive circuitry responsive to an analog signal received at the second port for converting said analog signal to a digital signal applied to said first port and for developing a maximum value N for said digital signal when said analog signal reaches a maximum analog level having a first magnitude, where N is an integer; and transmit circuitry for applying an analog signal corresponding to a digital signal received at said first port and applied to the transmit circuitry, where the analog signal applied by said transmit circuitry to the second port has level of a second magnitude, where said second magnitude is at least twice as large as the first magnitude, and where the maximum magnitude of the analog signal developed by the transmit circuitry is developed in response to a value of N of the digital signal applied to the transmit circuitry, thus the analog signal received by said receive circuitry is characterized by a small dynamic range compared to the analog signal developed by the transmit circuitry, and the analog signal developed by said transmit circuitry is characterized by a large dynamic range compared to the analog signal received by the receive circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for communicating a digital signal, comprising the steps of:
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converting the digital signal to an analog signal having a first maximum analog level, developing a digital signal responsive to said analog signals, where said digital signal corresponds to said analog signal but with an attenuated maximum level, achieving thereby a mapping from the digital signal applied to said step of converting to the digital signals created by said step of developing a digital signal to uniquely relate each value at the input to the step of converting with a unique output of the step of developing for assisting in cancelling an echo signal. - View Dependent Claims (9, 10, 11)
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Specification