88.7 All of the information transmitted in a DSC distress alert is decoded and displayed on other DSC-capable receivers scanning the frequency/ channel and is accompanied by an audible alarm to alert the operator. The broadcast of the radiotelephony distress call and message on a radiotelephony frequency/channel further alerts and advises stations of the distress situation. Steps to transmit a DSC distress alert and subsequent distress call and message.
Select DSC Distress Channel
Initiate DSC Distress Alert
Change to Associated Radiotelephony channel
Transmit Radiotelephony Distress Call and Message
89. ACKNOwLeDGEMeNT OF ReCeIPT OF A DSC DISTReSS ALeRT ON 2187.5 KHz OR VHF CHANNeL 70 89.1 Ship stations receiving a distress alert from another vessel on 2187.5 kHz or VHF channel 70 should take note of the contents and immediately listen on 2182 kHz or VHF Channel 16 for the MAYDAY message that should follow. 89.2 If the MAYDAY message is received, and the receiving ship is able to provide assistance, then a radiotelephony acknowledgement (ReCeIVeD MAYDAY, see paragraph 130) should be sent to the distressed vessel on 2182 kHz or VHF channel 16, and an appropriate Maritime Communication Station or Limited Coast Station advised. 89.3 If the receiving ship is not able to provide assistance, and other stations are heard indicating involvement in the distress situation, then no acknowledgement should be sent. 89.4 In situations where a ship station has received a DSC distress alert on 2187.5 kHz or VHF channel 70 and a) no MAYDAY message has been heard on 2182 kHz or VHF channel 16 within 5 minutes; b) no other station is heard communicating with the distressed vessel; and c) the DSC distress alert continues to be received; then the ship which received the DSC distress alert should transmit a radiotelephony acknowledgement, substituting the distressed vessel’s MMSI for its name and call sign, if necessary. Immediately following this, the receiving ship must contact an appropriate Maritime Communication Station or Limited Coast Station and fully advise it of the situation. 89.5 In situations where a ship station has received a DSC distress alert on 2187.5 kHz or VHF channel 70 and no MAYDAY message has been heard on 2182 kHz or VHF channel 16 within 5 minutes; and a) no other station is heard communicating with the distressed vessel; and b) the DSC distress alert is not continuing then no acknowledgement should be sent. The receiving ship should immediately contact an appropriate Maritime Communication Station or Limited Coast Station and fully advise it of the situation.
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MARINE RADIO OPERATORS HANDBOOK