Answer-originate data communication system

Claim 2

A data system for communication over the standard type of telephone line in the answer or originate modes at interchangeable frequencies to a time shared computer, Teletype, or other data line comprising: a telephone handset operable to receive an acoustical dual frequency signal, a carrier detector having a predetermined level output representative of a suitable carrier level, means coupling said carrier detector to said telephone signal including an originate and an answer line filter, a limiter also connected to said coupling means for converting said carrier signal to a constant-amplitude noise-free signal, said limiter including an integrated circuit operational amplifier with feedback circuit comprising a pair of transistors in a bridge configuration to limit signals to a predetermined level and to provide a signal of constant amplitude, an originate discriminator and an answer discriminator for detecting said dual frequency signal to produce a bipolar output signal corresponding to the data received, a slicer operable to increase the signal-to-noise ratio of said discriminated signal and to produce a squarewave output, a Teletype driver for combining the data signal from said slicer and the carrier present signal from said carrier detector with that of preselected keyboard signals, a transmit section including an originate oscillator and an answer oscillator for generating a dual frequency signal, means for providing said dual frequency signal to said transmit section for duplex operation, a plurality of field effect transistor switching circuits, including a first and second field effect transistor switching circuit for said originate discriminator and said answer discriminator, and a third and fourth field effect transistor switching circuit for said originate oscillator and said answer oscillator; said switching circuits operable to activate interchangeably said discriminators and said oscillator and a fifth and sixth field effect transistor switching circuit for said originate line and answer line filters.

Claim 3

A data communication system as set forth in claim 1 wherein said originate and an answer line filter further comprises: a preamplifier, and an originate and answer receiver filter; said line filterS having component parameters to provide a steeper attenuation on the input relative to that of the output, whereas said receive filters component parameters provide a steeper attenuation on the output relative to that of the input; and means interconnecting said preamplifier between aid line and receive filters.

Claim 4

A data communication system as set forth in claim 1 wherein said switching circuits comprise a seventh and eighth field effect transistor switching circuit for said originate/receive and answer/receive filters.

Claim 5

A data communication system as set forth in claim 1 further comprising means for coupling said discriminator circuits to the output of said limiter circuit and to the input of said slicer circuit, and wherein said discriminator coupling means further comprises said second and third field effect switching circuit.

Claim 6

A data communication system as set forth in claim 1 further comprising a delay timer interconnecting said carrier detector to said Teletype driver, said delay timer operable to provide a predetermined delay of said carrier signal prior to applying same to said driver.

Claim 7

A a data system for communication over the standard type of telephone line in the answer or originate modes at interchangeable frequencies to a time shared computer, a Teletype, or other data line comprising: a telephone handset operable to receive an acoustical dual frequency signal, a carrier detector having a predetermined level output representative of a suitable carrier level, means coupling said carrier detector to said telephone signal including an originate and an answer line filter, a limiter also connected to said coupling means for converting said carrier signal to a constant-amplitude noise-free signal, an originate discriminator and an answer discriminator for detecting said dual frequency signal to produce a bipolar output signal corresponding to the data received, a slicer operable to increase the signal-to-noise ratio of said discriminated signal and to produce a squarewave output, a Teletype driver for combining the data signal from said slicer and the carrier present signal from said carrier detector with that of preselected keyboard signals, a transmit section including an originate oscillator and an answer oscillator for generating a dual frequency signal, means for providing said dual frequency signal to said transmit section or duplex operation, a first and second switching circuit for said originate discriminator and said answer discriminator, and a third and fourth switching circuit for said originate oscillator and said answer oscillator; said switching circuits operable to activate interchangeably said discriminators and said oscillator; an automatic answer hold-off circuit including an abort timer and an interface circuit, said abort timer operative after a predetermined period to hold off or on said interface circuit dependent upon the receipt of data or not; and wherein said interface circuit further comprises a transistor circuit, means connecting said timer signal and said carrier detector signal to the base of said transistor, said transistor circuit rendered conducting upon the receipt of said timer signal and said carrier signal.

Claim 8

A a data system for communication over the standard type of telephone line in the answer or originate modes at interchangeable frequencies to a time shared computer, a Teletype, or other data line comprising: a telephone handset operable to receive an acoustical dual frequency signal, a carrier detector having a predetermined level output representative of a suitable carrier level, means coupling said carrier detector to said telephone signal including an originate and an answer line filter, a limiter also connected to said coupling means for converting said carrier signal to a constant-amplitude noise-free signal, an originate discriminator and an answer discriminator for detecting said dual frequency signal to produce a bipolar output signal corresponding to the data received, a slicer operable to increase the signal-to-noise ratio of said discriminated signal and to produce a squarewave output, a Teletype driver for combining the data signal from said slicer and the carrier present signal from said carrier detector with that of preselected keyboard signals, a transmit section including an originate oscillator and an answer oscillator for generating a dual frequency signal, means for providing said dual frequency signal to said transmit section or duplex operation, a first and second switching circuit for said originate discriminator and said answer discriminator, and a third and fourth switching circuit for said originate oscillator and said answer oscillator; said switching circuits operable to activate interchangeably said discriminators and said oscillator; an automatic answer hold-off circuit including an abort timer and an interface circuit, said abort timer operative after a predetermined period to hold off or on said interface circuit dependent upon the receipt of data or not; and wherein said interface circuit further comprises a transistor circuit, means connecting said timer signal and said carrier detector signal to the base of said transistor, said transistor circuit rendered conducting upon the receipt of said timer signal and said carrier signal.

Claim 9

A data communication system as set forth in claim 6 wherein said abort timer is initiated by the receipt of the telephone ring and operative after a predetermined time to disconnect the telephone line in the absence of the receipt of data.

Claim 10

A data communication system as set forth in claim 6 wherein a relay circuit is connected between the line ring input and said abort timer, said circuit adjusted to prevent said initiation of said abort timer unless a full ring cycle is received.

Claim 11

A data communication system as set forth in claim 6 further comprising a manual mode for maintaining at all times line voltage to said answer circuits.

Claim 12

A data communication system as set forth in claim 6 wherein said abort timer comprisEs a resistive and capacitive network.

Claim 13

A a data system for communication over the standard type of telephone line in the answer or originate modes at interchangeable frequencies to a time shared computer, a Teletype, or other data line comprising: a telephone handset operable to receive an acoustical dual frequency signal, a carrier detector having a predetermined level output representative of a suitable carrier level, means coupling said carrier detector to said telephone signal including an originate and an answer line filter, a limiter also connected to said coupling means for converting said carrier signal to a constant-amplitude noise-free signal, an originate discriminator and an answer discriminator for detecting said dual frequency signal to produce a bipolar output signal corresponding to the data received, a slicer operable to increase the signal-to-noise ratio of said discriminated signal and to produce a squarewave output, a Teletype driver for combining the data signal from said slicer and the carrier present signal from said carrier detector with that of preselected keyboard signals, a transmit section including an originate oscillator and an answer oscillator for generating a dual frequency signal, means for providing said dual frequency signal to said transmit section for duplex operation, a first and second switching circuit for said originate discriminator and said answer discriminator, and a third and fourth switching circuit for said originate oscillator and said answer oscillator; said switching circuits operable to activate interchangeably said discriminators and said oscillator; a power supply and a terminal control circuit connected thereto, an answer circuit, and an automatic answer hold-off circuit; said answer circuit operative upon the receipt of a ring signal, said answer circuit connected to said terminal control for applying, when operative, power from said supply to said terminal control.

Claim 14

A a data system for communication over the standard type of telephone line in the answer or originate modes at interchangeable frequencies to a time shared computer, a Teletype, or other data line comprising: a telephone handset operable to receive an acoustical dual frequency signal, a carrier detector having a predetermined level output representative of a suitable carrier level, means coupling said carrier detector to said telephone signal including an originate and an answer line filter, a limiter also connected to said coupling means for converting said carrier signal to a constant-amplitude noise-free signal, an originate discriminator and an answer discriminator for detecting said dual frequency signal to produce a bipolar output signal corresponding to the data received, a slicer operable to increase the signal-to-noise ratio of said discriminated signal and to produce a squarewave output, a Teletype driver for combining the data signal from said slicer and the carrier present signal from said carrier detector with that of preselected keyboard signals, a transmit section including an originate oscillator and an answer oscillator for generating a dual frequency signal, means for providing said dual frequency signal to said transmit section for duplex operation, a first and second switching circuit for said originate discriminator and said answer discriminator, and a third and fourth switching circuit for said originate oscillator and said answer oscillator; said switching circuits operable to activate interchangeably said discriminators and said oscillator; a power supply and a terminal control circuit connected thereto, an answer circuit, and an automatic answer hold-off circuit; said answer circuit operative upon the receipt of a ring signal, said answer circuit connected to said terminal control for applying, when operative, power from said supply to said terminal control.

Claim 15

A data communication system as set forth in claim 11 wherein said terminal control circuit comprises a transistor and an interconnecting relay.