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Telecom equipment works with DC power. The voltage levels are generally 48V or in a few cases 24V. A typical rectifier converts the AC utility power to 48 V DC, charging a bank of batteries usually designed for two to eight hours of critical protection from power outage.

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Posted by sagitraz

telephonyonline.com/news/telecom_great_acdc_debate

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Posted by crouse

www.liebert.com/topissue_pages/top_issues.aspx?x=voip

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Posted by crouse

AC power system is required for voice and data communication.

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Posted by eric

DC-48 V

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Posted by HamidAliKhan

Telecom equipment works with DC power. The voltage levels are generally 48V or in a few cases 24V. A typical rectifier converts the AC utility power to 48 V DC, charging a bank of batteries usually designed for two to eight hours of critical protection from power outage. Since a battery bank is floated across the DC bus, to provide battery backup, the working voltage is in reality the float voltage of the battery. For VRLA batteries, the float voltage is typically 2.25V/cell or 54V for a 48V system and 27V for a 24V system. The positive in a 48V system is grounded, whereas in a 24V system, the negative is grounded. This difference is due to the practice adopted by the pioneering telecom equipment manufacturers, which is continuing today. In contrast to AC systems, DC systems do not require converting the source power from AC/DC and DC/AC.

From:http://voicendata.ciol.com/content/goldbook/goldbook03/103033111.asp

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Posted by sagitraz