Telephone line circuit and system
Patent 4456991 Issued on June 26, 1984. Estimated Expiration Date: 
January 10, 2003. 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.
January 10, 2003. 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 References 3617643 Time-division-multiplexed exchanger Control information communication arrangement for a time division switching system Signal monitoring and controlling system in a time division switching system Automatic digital telephone exchange Time division electronic switching system Patent #: 4370742 Inventors
ApplicationNo. 06/456638 filed on 01/10/1983US Classes:370/359, Input or output circuit, per se (i.e., line interface)379/339, With signal conversion (e.g., dial to DTMF, analog to PCM)379/340, Having line length compensation or equalization379/345, Including two-to-four wire conversion or hybrid circuit379/382, For ring trip or polarity reversal detection379/394Impedance matching or line equalizingExaminersPrimary: Olms, Douglas W.Attorney, Agent or FirmInternational ClassH04Q 11/04 (20060101)AbstractA telephone line circuit and system for interfacing digital exchange line circuits to a terminal interface of a switching network is disclosed. The system includes controllable active circuit impedance matching means for reducing impedance mismatch between a selected line circuit and the terminal interface. Control means controls both the active circuit impedance matching means for adjusting the effective circuit impedance to a value within a predetermined range, and the conditioning circuit gain pads for selectably adjusting the gain of a transmitted signal. Additionally, control means controls the d.c. line impedance and voltage for adjusting the effective line feed current to the subscriber loop, and provides interfaces for a plurality of line circuits to both a switching network and external processor. Supervision means provides supervision control signals to the control means and thereby permits the telephone line circuit system to provide desired telephone system functions. | |
