The Global Maritime Distress and Safety System (GMDSS) is an internationally agreed set of safety procedures, types of equipment, and communication protocols to ensure the safety of ships and facilitate search and rescue activities for ships, boats, or aircraft in distress.

GMDSS consists of several new or existing systems that have been in operation for several years. These systems are intended to: issue alerts (including the position of the unit in distress), coordinate search and rescue, enable locating, disseminate maritime safety information, provide general communications, and enable ship-to-ship communication/communication with emergency call centres. These systems must also have a secondary backup for distress signalling purposes and emergency power supply.

NAVTEX (NAVigational TEleX), also known as Navtex or NavTex, is an international low-frequency automated printing service for disseminating navigational information, meteorological warnings and forecasts, as well as maritime safety information (MSI) to ships. Navtex is provided to offer an inexpensive, straightforward, and automatic information reception service onboard ships within a range of 370 km (200 nautical miles) from land.

Digital selective calling or DSC is a standard for sending digital messages using the medium frequency (MF), high frequency (HF), and very high frequency (VHF) channels of the maritime radio system. It is one of the main pillars of the Global Maritime Distress Safety System (GMDSS).