RTCM 11901.2, Standard for Maritime Survivor Locating Devices (MSLD) November 15, 2024

Maritime Survivor Locating Devices (MSLD) traditionally consisted of an alerting unit with a transmitter module, an integral antenna, and a power source, all contained in a wearable watertight case. The alerting unit is typically used with a base unit on a vessel, but may be used with an existing receiver suited for the purpose. In addition, a locating unit is often included, which may or may not be part of the base unit.

Alerting units are intended to be carried by individuals engaged in on-deck activities on vessels, or in activities on shore where falls into the water are a risk, or in other marine activities where location of persons may be required. The purpose of the AU is to send a local alert primarily to a base unit on one's own vessel or facility, and possibly also to base units on other vessels nearby. The alerting unit may also serve as a locating beacon to assist in the individual's recovery.

Modern MSLDs described in this latest version of the standard accounts for several technologies and combinations of alerting now available.   MSLDs may include DSC, AIS, 121.5 MHz homing, PLB, and SENDs technologies.  Performance and test standards for the internal navigation device (such as a GPS receiver) that is necessary for the AIS version is also included.  The standard added a Suitability by Activity and Region table to assist readers in evaluating the technologies most appropriate for their use cases.