Also known as: DSC
DSC (Digital Selective Calling) is a maritime protocol for calling specific stations and broadcasting distress alerts. Part of the Global Maritime Distress and Safety System (GMDSS), it sends short FSK data bursts on VHF channel 70 (156.525 MHz) and on HF.1
Overview
A DSC message carries the sender’s and (for selective calls) recipient’s MMSI, a category (routine, safety, urgency, distress), and optional position. A distress alert automatically conveys identity and, if interfaced, GPS position. DSC complements AIS on the safety side.
Technical characteristics
| Property | Value |
|---|---|
| Band | VHF Ch 70 + HF DSC frequencies |
| Modulation | FSK burst |
| Addressing | MMSI |
| Error control | Symbol repetition + parity |
History
Standardised by the ITU and mandated within GMDSS from the 1990s to modernise distress alerting beyond voice calling.1
Deployment
SOLAS and recreational vessels, coast stations, and rescue coordination centres.
Decoding it with GopherTrunk
GopherTrunk demodulates the FSK, applies the symbol-repetition error control, and decodes DSC messages. See the DSC decoder page.
Sources
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Digital selective calling — Wikipedia, for the maritime DSC protocol within GMDSS, VHF channel 70 signalling, MMSI addressing, and distress alerting. ↩ ↩2