An apparatus or corresponding method of managing Plain Old Telephone Service (POTS) lines in a Passive Optical Network (PON) to prevent an alarm system from generating an alarm during a software upgrade or maintenance of an Optical Network Terminal (ONT), Optical Line Terminal (OLT), or PON while maintaining the effectiveness of the alarm system. The ONT may store data related to a POTS line in nonvolatile memory. The ONT may activate the POTS line based on the data from the nonvolatile memory in an event of interruption in communications with an OLT prior to reestablishing communications with the OLT. The interruption in communications may be caused by an ONT reboot to complete an installation of a software upgrade. The ONT may energize the POTS line with a voltage in response to activating the POTS line to prevent the alarm system from generating the alarm.