Switchable line powered modem
First Claim
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1. A telephone modem comprising:
- a modem transmitter subsystem operative in response to data from a source to provide modulated data signals to the telephone line;
a modem receiver subsystem operative to provide data signals derived from signals received on the telephone line including a filter selectively providing in response to a mode control signal, a band-pass characteristic in one of two operating frequency bands and selectively providing in response to said mode control signal, a band-rejection characteristic in the other of the two operating frequency bands wherein the selected band-pass characteristic includes a range of frequencies exclusive of the band-rejection characteristic range of frequencies; and
control means operative to select either of two frequency bands for transmission and reception and for providing the mode control signal,wherein said receiver subsystem filter comprises a switchable feedback network band-pass filter providing in response to said mode control signal, a predetermined band-pass characteristic having at least one relative signal amplitude peak in the one of two frequency bands of interest, and a simultaneous band rejected characteristic having at least one relative signal amplitude notch in the other of two frequency bands of interest,wherein the filter circuit feedback network includes switch means which alter the feedback network topology to provide the selection of band-pass and band-reject characteristic from among the particular frequency bands of interest.
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Abstract
A modem for coupling a data terminal or other apparatus to a telephone line and deriving its operating power for both transmitting and receiving operation from the telephone line, and providing electrical isolation between the telephone line and the data terminal. The modem is switchable to provide orginate or answer operation in either of two operating frequency bands.
143 Citations
18 Claims
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1. A telephone modem comprising:
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a modem transmitter subsystem operative in response to data from a source to provide modulated data signals to the telephone line; a modem receiver subsystem operative to provide data signals derived from signals received on the telephone line including a filter selectively providing in response to a mode control signal, a band-pass characteristic in one of two operating frequency bands and selectively providing in response to said mode control signal, a band-rejection characteristic in the other of the two operating frequency bands wherein the selected band-pass characteristic includes a range of frequencies exclusive of the band-rejection characteristic range of frequencies; and control means operative to select either of two frequency bands for transmission and reception and for providing the mode control signal, wherein said receiver subsystem filter comprises a switchable feedback network band-pass filter providing in response to said mode control signal, a predetermined band-pass characteristic having at least one relative signal amplitude peak in the one of two frequency bands of interest, and a simultaneous band rejected characteristic having at least one relative signal amplitude notch in the other of two frequency bands of interest, wherein the filter circuit feedback network includes switch means which alter the feedback network topology to provide the selection of band-pass and band-reject characteristic from among the particular frequency bands of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A telephone line powered modem comprising:
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a first circuit for coupling to a telephone line and operative wholly in response to telephone line power for all modem circuits; a modem transmitter subsystem powered by the first circuit and operative in response to data from a source to provide modulated data signals to the telephone line; a modem receiver subsystem powered by the first circuit and operative to provide data signals derived from signals received on the telephone line, including a switchable band-pass filter providing in response to a mode control signal, a predetermined band-pass characteristic in one and simultaneously a band-reject characteristic exhibits a notch in the other of two respective different operating bands, the selection of which bands are occupied by the band-pass and band-reject characteristics is made by selectable feed-back paths within said switchable band-pass filter; and control means powered by the first circuit and operative to select either of two operating frequency bands for transmission and reception.
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18. For use in a telephone line powered modem which includes a receiver operative to provide data signals derived from signals received on a telephone line, and a transmitter operative in response to data from a source to provide modulated data signals for transmission on the telephone line, a switchable filter operative wholly in response to telephone line power and comprising:
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at least one active filter comprising a feedback network which includes solid state low power switch means; in a first switch mode the filter exhibits a band-pass characteristic in one band of frequencies and a band-reject characteristic in another band of frequencies; in a second switch mode the filter exhibits the band-pass characteristic in the other band of frequencies and the band-reject characteristic in the one band of frequencies; wherein the band-reject characteristic exhibits a notch.
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Specification