Interface circuit
Patent 4894864 Issued on January 16, 1990. Estimated Expiration Date: 
July 14, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
July 14, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesTelephone subscriber line unit with sigma-delta digital to analog converter Automatic, digitally synthesized matching line terminating impedance Hybrid circuit Full duplex speakerphone for radio and landline telephones Patent #: 4629829 InventorAssigneeApplicationNo. 095573 filed on 07/14/1987US Classes:379/398, LINE EQUALIZATION OR IMPEDANCE MATCHING379/340, Having line length compensation or equalization379/399.02Circuitry to provide a coder and decoder functionExaminersPrimary: LaRoche, Eugene R.Assistant: Lee, Benny Attorney, Agent or FirmForeign Patent References
International ClassH04B 003/03Foreign Application Priority Data1985-11-22 GBAbstractAn analog/digital interface circuit in which an analog terminating impedance is partially synthesized by supplying a digital output (T) signal to a digital input (R) via a digital filter (17). A variable resistive transmission path is connected across the analog ports the resistance of which may be varied along with characteristics of the digital filter in order to simulate any required terminating impedance. The structure facilitates changing ZT while maintaining the required frequency response and remaining stable.Other References
Field of SearchLINE EQUALIZATION OR IMPEDANCE MATCHINGFor line length compensation Hybrid circuit With adjustable balance circuit Automatic adjustment Electronic noninductive Power supply (e.g., battery feed) Having line length compensation or equalization Including two-to-four wire conversion or hybrid circuit | |
