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US 5,179,586 AGranted
Line interface circuit
AssigneeNorthern Telecom Limited
InventorMichael C. G. Lee
Life of this patent
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AssigneeNorthern Telecom Limited
InventorMichael C. G. Lee
Estimating the term…
An interface unit for interconnecting a telephone central switch to a personal computer. The interface unit receives power and data from the switch over a two wire twisted pair. The data is in a half duplex T.C.M. format and is transformed into standard digital data with the logic "1" and "0" being represented by +5V and 0V respectively. The standard digital data is then arranged into 8 bit words and encoded in either an asynchronous or synchronous manner depending on the type of computer. The interface unit has a line interface circuit which provides the physical interface between the interface unit and the computer. The interface unit has a transmitter circuit which converts the +5V and 0V digital signals to -5V and +5V, respectively. These values are recognized by the computer as logic "1" and "0". The interface unit also has a receive circuit which takes the computer output signals (between -5 and -12V for logic "1" and between +5 and +12V for logic "0") and converts them back into standard digital format.
An interface circuit for converting first digital data in which binary "1"s and "0"s are defined by first and second voltage levels respectively into a data signal in which the binary "1"s and "0"s are defined by third and fourth voltage levels, respectively, the interface circuit comprising a first current source deriving a voltage at the third voltage level and a second current source deriving a voltage source at the fourth voltage level and means for connecting the first current source to an output when the digital data is at the first voltage level and for connecting the second current source to the output when the digital data is at the second voltage level.
An interface circuit for converting first digital data in which binary "1"s are defined by a first voltage ranging between a first two levels and binary "0"s are defined by a second voltage ranging between a second two levels into a data signal in which the binary "1"s and "0"s are defined by third and fourth voltage levels, the interface circuit comprising a level translator and inverter for setting an output voltage to the third voltage level when the incoming voltage is between the first two levels and for setting the output voltage to the fourth voltage level when the incoming voltage is between the second two levels.
An interface circuit for connecting a telephone interface unit in which digital data represented by +5V for logic "1" and 0V for logic "0" is present is present to a personal computer in which logic "1" is represented by at least -5V and logic "0" is represented by at least +5V, the interface unit comprising a transmitter circuit having a first current source connected to +5V and a second current source connected to -5V and means for connecting the first current source to the computer when the digital data is 0V and connecting the second current source to the comparator when the digital data is +5V, the interface unit comprising a receiver circuit for producing an output voltage of +5V when data received from the personal computer is at least -5V and for producing an output voltage of 0V or when data received from the personal computer is at least +5V.
A telephone interface unit for interconnecting a telephone central switch to a personal computer, the interface unit comprising terminal means for connection of a power/data line from the central switch, a power supply powered by the power/data line, means for connecting TCM data on the power/data line to digital data and vice versa, where the digital data is in one of a UART format and an HDLC format with logic "1" represented by +5V and logic "0" represented by 0V and an interface circuit for connecting the interface unit to the personal computer, the interface circuit comprising a transmitter circuit having a first current source connected to +5V and a second current source connected to -5V and means for connecting the first current source to the computer when the digital data is 0V and connecting the second current source to the comparator when the digital data is +5V, the interface unit comprising a receiver circuit for producing an output voltage of +5V when data received from the personal computer is at least -5V and for producing an output voltage of 0V or when data received from the personal computer is at least +5V.
Dependencies are inferred from the claim text.