Interface means
Patent 5151936 Issued on September 29, 1992. Estimated Expiration Date: 
May 29, 2010. 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.
May 29, 2010. 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 ReferencesDuplex telephone signalling system Detector circuit for sensing battery polarity and loop closure Interface for private branch exchange Loop-start/ground-start line interface circuit Universal DC signalling detector Universal PBX interface PBX voice mail interface Patent #: 4930153 InventorAssigneeApplicationNo. 529613 filed on 05/29/1990US Classes:379/403, With adjustable balance circuit379/402Hybrid circuitExaminersPrimary: Dwyer, James L.Assistant: Augustus, Jhancy Attorney, Agent or FirmForeign Patent References
International ClassH04M 009/00Foreign Application Priority Data1989-05-31 DEAbstractAn interface between a bidirectional transmission channel with analog signals and four-wire input of a digital communication system. In order to enable a formatting of the interface as an integrated module in 10 V technology, a repeater or transformer is operated as an attenuation element in a lower frequency range and the transmission or, respectively, terminating impedance is selected such that all signalization voltages are transformed into a range that can be evaluated in 10 V technology, whereby, for suppressing higher-frequency noise signals, the signalization voltages are supplied via a low-pass filter to a ringing signal detector or, respectively, via a selective band-pass filter to a call charge signal detector.Other References
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