igital-clock-period jitter is the variation in the period of a clock cycle compared with a nominal (average of many cycles) clock period.To accurately measure period jitter using an oscilloscope, you must subtract the oscilloscope jitter from the measured jitter.
http://www.edn.com/article/CA158989.html
PLC transmits data over an existing high-voltage power line instead of requiring dedicated cabling. PLC can thus provide an inexpensive solution for transmitting data in a pre-wired location.
http://focus.ti.com/docs/solution/folders/print/306.html
The MAX2980 powerline communication analog frontend (AFE) integrated circuit (IC) is a state-of-the-art CMOS device that delivers high performance and low cost.
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4032
How to get powerline communication signals from one mains phase to another.
http://hometoys.com/htinews/jun97/articles/kingery/kingery3.htm