Synchronized or unsynchronized partial response binary signalling

Claim 3

The method according to claim 1 in which said filtering of said binary NRZ wave is performed with a linear phase-frequency characteristic and an amplitude response function of

Claim 4

A facsimile transceiver for use with voice telephone circuits comprising: a scanner-printer unit operable to scan in synchronism with a remote similar unit; optical means in said unit operable for analyzing a document at a predetermined rate and resolution to produce a scan line signal corresponding to a maximum transition rate of approximately 4,000 transitions per second; quantizing means responsive to said scan line signal for producing a binary non-return to zero (NRZ) wave having transitions at the black-white transitions of the scan line on said document; filter means responsive to said binary NRZ wave with an amplitude response where f1 is approximately 2.17 kc and a linear phase-frequency characteristic for producing a partial response binary wave; a stable oscillator; means for deriving a carrier wave from said oscillator of frequency approximately 2.4 kc; means for baseband balanced amplitude modulating said carrier wave with said partial response binary wave to produce a modulated carrier wave; means operable for coupling said modulated carrier wave to a telephone line; means operable for coupling a modulated carrier wave from a telephone line connection with said remote similar unit; amplifier and transversal filter means responsive to the signal coupled from said telephone line for equalizing and correcting system and phone line distortion in the signal received from said remote unit; envelope detector means responsive to the signal from said amplifier and transversal filter means for detecting said partial responsive binary wave; slicer means responsive to said partial response binary wave with threshold detection centered on said partial binary response wave for obtaining a replica of said binary NRZ wave; and means for applying said replica of said binary NRZ wave to said scanner-printer unit to print a facsimile copy of the document scanned at said remote similar unit.

Claim 5

A facsimile transceiver for use with voice telephone circuits comprising: a scanner-printer unit operable to scan in synchronism with a remote similar unit; optical means in said unit operable for analyzing a document at a predetermined rate and resolution to produce a scan line signal corresponding to a maximum transition rate of approximately 4,000 transitions per second; quantizing means responsive to said scan line signal for producing a binary non-return to zero (NRZ) wave having transitions at the black-white transitions of the scan line on said document; filter means responsive to said binary NRZ wave with an amplitude response where f1 is approximately 2.17 kc and a linear phase-frequency characteristic for producing a partial response binary wave; a stable oscillator; means for deriving a carrier wave from said oscillator of frequency approximately 2.4 kc; means for baseband balanced amplitude modulating said carrier wave with said partial response binary wave to produce a modulated carrier wave; means operable for coupling said modulated carrier wave to a telephone line; means operable for coupling a modulated carrier wave from a telephone line connection with said remote similar unit; amplifier and transversal filter means responsive to the signal coupled from said telephone line for equalizing and correcting system and phone line distortion in the signal received from said remote unit; envelope detector means responsive to the signal from said amplifier and transversal filter means for detecting said partial responsive binary wave; slicer means responsive to said partial response binary wave with threshold detection centered on said partial binary response wave for obtaining a replica of said binary NRZ wave; and means for applying said replica of said binary NRZ wave to said scanner-printer unit to print a facsimile copy of the document scanned at said remote similar unit.

Claim 6

A transceiver according to claim 3 and including: means responsive to the initiation of transmission from a document for sending for a limited interval a signal modulated at a level representing the mid-amplitude of said quantizer output; and means responsive to the initial reception of a modulated carrier for adjusting during said interval the slicing threshold of said slicing means to correspond to the level of said modulation.

Claim 7

Apparatus according to claim 4 in which the slicing threshold adjusting means comprises: a gain control for said amplifier and transversal filter means; a degenerative feedback control circuit responsive to the output of said slicer for adjusting said gain control; and means for maintaining the adjusted level for said gain control after said interval.

Claim 8

A modem for transmitting data over voice telephone circuits comprising: means for deriving said data as a binary non-return to zero (NRZ) wave having a maximum transition rate of approximately 4, 000 transitions per second; filter means responsive to said binary NRZ wave having a linear phase frequency characteristic and an amplitude response where f1 is approximately 2.17 kc for producing a partial resPonse binary wave; means for supplying said partial response binary wave to a transmission terminal for transmission over said telephone circuits; means for receiving said partial response binary wave from a telephone circuit; and slicer means responsive to said partial response binary wave with threshold detection centered on said partial response binary wave for obtaining a replica of said binary NRZ wave.

Claim 9

A modem for transmitting data over voice telephone circuits comprising: means for deriving said data as a binary non-return to zero (NRZ) wave having a maximum transition rate of approximately 4, 000 transitions per second; filter means responsive to said binary NRZ wave having a linear phase frequency characteristic and an amplitude response where f1 is approximately 2.17 kc for producing a partial resPonse binary wave; means for supplying said partial response binary wave to a transmission terminal for transmission over said telephone circuits; means for receiving said partial response binary wave from a telephone circuit; and slicer means responsive to said partial response binary wave with threshold detection centered on said partial response binary wave for obtaining a replica of said binary NRZ wave.

Claim 10

A modulation circuit for transmitting data over voice telephone circuits comprising: means for deriving said data as a binary non-return to zero (NRZ) wave having a maximum transition rate of approximately 4, 000 transitions per second; filter means responsive to said binary NRZ wave having a linear phase frequency characteristic and an amplitude response where f1 is approximately 2.17 kc for producing a partial response binary wave; and means for supplying said partial response binary wave to a transmission terminal for transmission over said telephone circuits.

Claim 11

A modulation circuit for transmitting data over voice telephone circuits comprising: means for deriving said data as a binary non-return to zero (NRZ) wave having a maximum transition rate of approximately 4, 000 transitions per second; filter means responsive to said binary NRZ wave having a linear phase frequency characteristic and an amplitude response where f1 is approximately 2.17 kc for producing a partial response binary wave; and means for supplying said partial response binary wave to a transmission terminal for transmission over said telephone circuits.

Claim 12

In a binary facsimile system having sending and receiving equipment for respectively scanning a document and reproducing a replica of the image pattern on the document wherein the scan signal is derived in the form of a binary signal representing the black and white image areas on said document, the binary signal being applied to modulate a carrier wave for transmission to said receiving equipment where the modulated carrier wave is demodulated to recover a binary signal which is used to produce said replica, the improvement comprising: means for generating a modulation signal at the transmitting equipment having a value for a modulation characteristic intermediate the values of said characteristic representing black and white on said document; means operative for a brief interval prior to each facsimile transmission for modulating said carrier wave with the intermediate value of said modulation signal; means for processing the demodulated signal in said receiving equipment for evaluating said characteristic of the modulation signal relative to a predetermined threshold value used to recover a binary replica of said binary signal; and means responsive to the relative evaluation of said modulation signal and said threshold value during said brief interval for setting the gain of said receiving equipment at a level which makes modulation levels different than said intermediate value fall unambiguously either above or below said threshold.

Claim 13

In a binary facsimile system having sending and receiving equipment for respectively scanning a document and reproducing a replica of the image pattern on the document wherein the scan signal is derived in the form of a binary signal representing the black and white image areas on said document, the binary signal being applied to modulate a carrier wave for transmission to said receiving equipment where the modulated carrier wave is demodulated to recover a binary signal which is used to produce said replica, the improvement comprising: means for generating a modulation signal at the transmitting equipment having a value for a modulation characteristic intermediate the values of said characteristic representing black and white on said document; means operative for a brief interval prior to each facsimile transmission for modulating said carrier wave with the intermediate value of said modulation signal; means for processing the demodulated signal in said receiving equipment for evaluating said characteristic of the modulation signal relative to a predetermined threshold value used to recover a binary replica of said binary signal; and means responsive to the relative evaluation of said modulation signal and said threshold value during said brief interval for setting the gain of said receiving equipment at a level which makes modulation levels different than said intermediate value fall unambiguously either above or below said threshold.

Claim 14

Apparatus according to claim 8 in which said modulation characteristic is the amplitude of said modulation signal and said carrier wave is amplitude modulated and in which the intermediate value of said modulation signal is a modulation amplitude approximately half way between the peak values of the modulation amplitude produced by said binary signal.

Claim 15

Means for transmitting and receiving data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, and an amplitude response to produce a partial response binary wave; and means for detecting said partial response binary wave to recover said data.

Claim 16

Means for transmitting and receiving data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, and an amplitude response to produce a partial response binary wave; and means for detecting said partial response binary wave to recover said data.

Claim 17

Means for transmitting data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; and means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, and an amplitude response

Claim 18

Means for transmitting data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; and means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, and an amplitude response

Claim 19

Means for transmitting and receiving data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, a smooth amplitude roll off which at frequency Kf1/2 is less than 40 percent of mid-band response, and which completes its response to each transition with negligible overshoot in no longer time than 2/Kf1 to obtain a partial response binary wave representing said binary NRZ wave; and means for detecting said partial response binary wave to recover said data.

Claim 20

Means for transmitting and receiving data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, a smooth amplitude roll off which at frequency Kf1/2 is less than 40 percent of mid-band response, and which completes its response to each transition with negligible overshoot in no longer time than 2/Kf1 to obtain a partial response binary wave representing said binary NRZ wave; and means for detecting said partial response binary wave to recover said data.

Claim 21

Means according to claim 12 in which said means for shaping the response of said channel comprises a filter having said transmittance function at the transmitting terminal.

Claim 22

Means for transmitting data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; and means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, a smooth amplitude roll off which at frequency Kf1/2 is less than 40 percent of mid-band response, and which completes its response to each transition with negligible overshoot in no longer time than 2/Kf1 to obtain a partial response binary wave representing said binary NRZ wave.

Claim 23

Means for transmitting data over a band limited channel having zero response above a frequency f1 comprising: means for applying said data to said channel as a binary non-return to zero (NRZ) wave having a maximum transition rate of Kf1 transitions per second where K approaches the value 2; and means for shaping the response of said channel such that the effective transmittance function has a linear phase-frequency characteristic, a smooth amplitude roll off which at frequency Kf1/2 is less than 40 percent of mid-band response, and which completes its response to each transition with negligible overshoot in no longer time than 2/Kf1 to obtain a partial response binary wave representing said binary NRZ wave.

Claim 24

Means according to claim 14 in which said means for shaping the response of said channel comprises a filter having said transmittance function at the transmitting terminal.