The Man Overboard Indicator (MOBI) system is a personal saltwater-activated man overboard (MOB) alarm system utilized by the US Navy and other mariners. The alarm system includes a transmitter, receiver and direction finder. A DSC (digital selective calling)-capable radio is also used with the TX-106 transmitter (p/n: ORCATX-106).

The TX-106 is worn on the MK-1 float coat and the inherently buoyant life preserver (IBLP) and transmits on 156.525 MHz and 121.5 MHz.  When activated, it emits an RF signal which calls the DSC-capable radio. The radio sounds upon receipt of this signal, indicating the identity and GPS coordinates of the MOB. The transmitter also emits a signal which is processed by the direction finder, providing a continuous bearing to the MOB.