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A transceiver capable of 6.25-Gb/s data transmission across legacy communications equipment backplanes is described. To achieve a bit error rate (BER) < 10-15, transmit and receive equalization that can compensate up to 20 dB of channel loss is employed to remove intersymbol interference (ISI) resulting from finite channel bandwidth and reflections. The transmit feed-forward equalizer (FFE) uses a four-tap symbol-spaced programmable finite impulse response (FIR) filter followed by a 4-bit digital-to-analog converter (DAC) that drives a 50-Ω transmission line. The receiver uses a half-baud-rate adaptive decision feedback equalizer (DFE) that cancels the first four symbol-spaced taps of postcursor ISI without use of speculative techniques. Both the transmitter and receiver use an LC-oscillator-based phase-locked loop (PLL) to provide low jitter clocks. Techniques to minimize the complexity of the FIR and DFE implementations are described. The transceiver is designed to be integrated in a standard ASIC flow in a 0.13-µm digital CMOS technology. System measurements indicate the ability to transmit and recover data eyes that have been fully closed due to crosstalk and signal loss. [ABSTRACT FROM AUTHOR]

Volunteering to help individuals with profound need or who might not have access to oral health care is part of the ethical fabric of the dental profession. This article describes examples from the spectrum of such programs, ranging from those sponsored by national, state, and component groups in organized dentistry to faith-based groups, collaborations with other health professions, and individual practitioners. The American Dental Association serves as a catalyst, support, and clearing house for such programs. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the editorial "The reality of nonscience-based newsletters," in the June 1996 issue.