電力線通信：一個(gè)可行的消費(fèi)者鏈接

　　電力線通信已經(jīng)存在了很長一段時(shí)間，我們大多數(shù)人最先接觸到這項(xiàng)技術(shù)，它早期用于家用自動(dòng)化和家電的遠(yuǎn)程控制。它使用交流電源線作為電源和通信介質(zhì)。

　　最初向公眾介紹了什么是現(xiàn)在被稱為X10協(xié)議，使用相同的導(dǎo)線，電源線通信的好處已經(jīng)得到很好的理解，這一技術(shù)擴(kuò)展用于電力公用事業(yè)，以及計(jì)算機(jī)網(wǎng)絡(luò)與分布式音頻流內(nèi)的建筑。

　　本文著眼于電力線通信技術(shù)和工程師可以用來實(shí)現(xiàn)它的設(shè)備。它檢查了一些歷史和流行的協(xié)議及其優(yōu)點(diǎn)和局限性，并討論了在決定電力線通信是否適合您的應(yīng)用程序時(shí)需要注意的問題。

　　From whence it came

　　The power utilities discovered early on that in addition to delivering raw high-voltage AC power through an extensive network of cables， switches， transformers， and circuit breakers， they also needed a way of communicating. In the 1920s and 1930s， people were not as dependent on electricity as they are today， so when power went out it could routinely take days or even weeks to send crews to find and fix power faults， especially in remote areas.

　　The most basic need for remote data gathering drove the early systems. The simplest implementations use narrow band 15 to 500 KHz carrier waves for rudimentary on/off keying for long haul remote data measurements over high tension power lines. These low-frequency RF signals are capacitively coupled at relatively low amplitudes （compared to the kilovolt levels of the AC power）， and do not interfere with the 60 Hz power and timing signals used in early electric appliances. （For example， before crystals， early clocks would get their time reference from the 60 Hz power line and high frequencies did not get through the transformers that converted the high-tension voltage to standard 120 volts used today）。