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<p>the positive terminal of power supply system and the <a href="page.php?w=battery_%28electricity%29">battery</a> bank. This is done to prevent <a href="page.php?w=electrolysis">electrolysis</a> depositions. Telephone installations have a battery system to ensure power is maintained for subscriber lines during power interruptions.</p>

<p>Other devices may be powered from the telecommunications DC system using a <a href="page.php?w=DC-DC_converter">DC-DC converter</a> to provide any convenient voltage.</p>

<p>Many <a href="page.php?w=telephone">telephone</a>s</p><p>
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