A power management circuit for use in a terminal interface device such as a modem which converts available line side power into usable power for use by the terminal interface device to activate a variety of line status indicators. These line status indicators signaling the off-hook status of the terminal...http://www.google.com/patents/US6724889?utm_source=gb-gplus-sharePatent US6724889 - Method and system for line status indicators using line side power
