Advanced Micro Devices Corporation

Leland Stanford Junior University

Hamid Najafi

Bruce B Lusignan

Disclosed is a digital phase-locked loop circuit for telecommunication circuits receiving bipolar codes. The digital phase-locked loop circuit includes a transition timer means for counting a transition duration between a high mark and a low mark in said bipolar code. A clock recovery signal is generated by dividing a transition duration by a value, such as two, to indicate an apparent zero crossing time, and comparing the apparent zero crossing time with the reference clock in the circuit receiving the bipolar code. The reference clock in the receiving circuit is adjusted in response to the clock recovery signal in order to maintain the reference clock substantially in phase with the incoming bipolar code.

Digital phase-locked loop circuit

A telephone line interface which performs the BORSHT functions employs pulse width modulation and eliminates dc in the transformer to reduce the size of the coupling transformer thereby reducing space and costs. The ring function is provided to the subscriber without use of mechanical relays. An automatic, dynamically adjusted hybrid network is provided for removing echo signals thereby providing major improvement in two-to-four wire conversion performance. The circuitry lends itself to large scale integration thereby reducing space and cost and improving reliability.

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Hamid Najafi