As of 2009, monitoring for distress signals in which frequency is scheduled to be terminated?

The correct choice is 121.5 MHz because, as of 2009, the monitoring of distress signals on this frequency was officially scheduled to be terminated by the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO). The 121.5 MHz frequency was widely used for emergency locator transmitters (ELTs) in aviation and for maritime distress calls. However, it was announced that the move toward the more modern and efficient 406.0 MHz frequency would provide better reliability and faster response times in search and rescue operations.

The 406.0 MHz signal is encrypted and transmits specific location information, which significantly improves the effectiveness of the search and rescue process. As a result, the older 121.5 MHz frequency has become obsolete for distress signal monitoring, reflecting advances in technology and changes in aviation and maritime safety protocols.