From http://tinyurl.com/men8bez
Relying upon rulings by decision makers such as Rabbi Shaul Yisraeli, Isser Yehuda Unterman and Rav Haim David HaLevi, the Zomet microphone uses only transistors "without any glowing [or 'burning'] elements;" is turned on by an automatic "Shabbat timer;" and, once turned on, "current flows continuously in the system," according to technical notes on the setup released on the group's website.
According to Zomet executive director Rabbi Dan Marans, the system has come into use in 15 synagogues in Baltimore, Montreal, West Stamford and other locations, as well as in 18 old-age homes. Leading American poskim, or decidors of Halacha, have even "stipulated in contracts with synagogues that they change the system to our system so that the RCA [will be] able to send rabbis."
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"I've not heard comments [against it]. If anything, people find the service more enjoyable and more elevating," agreed Schneier, adding that "We must get a dozen calls a year from rabbis contemplating putting this system into their synagogues.
"I believe within 25 years it will be commonplace in Orthodox synagogues here in the Northeast."
See the above URL for more. YL