The following procedures were adapted from the International Telecommunications Union, Radiocommunications Study Group Recommendation M.541, Operational Procedures for the use of Digital Selective-Calling (DSC) Equipment in the Maritime Mobile Service.
Operating procedures may vary somewhat among different radios, depending upon how the radio is designed, how the radio's software is configured, and how the DSC processor is connected to the radio transceiver.
Transmission of Urgency Messages
Transmission of urgency messages shall be carried out in two steps:
- announcement of the urgency message,
- transmission of the urgency message.
The announcement is carried out by transmission of a DSC urgency call on the DSC distress calling channel (2187.5 kHz on MF, channel 70 on VHF).
The urgency message is transmitted on the distress traffic channel (2182 kHz on MF, channel 16 on VHF).
The DSC urgency call may be addressed to all stations or to a specific station. The frequency on which the urgency message will be transmitted shall be included in the DSC urgency call.
The transmission of an urgency message is thus carried out as follows:
- tune the transmitter to the DSC distress calling channel (2 187.5 kHz on MF, channel 70 on VHF);
- key in or select on the DSC equipment keyboard:
- All Ships Call or the 9-digit identity of the specific station,
- the category of the call (urgency),
- the frequency or channel on which the urgency message will be transmitted,
- the type of communication in which the urgency message will be given (e.g. radiotelephony), in accordance with the DSC equipment manufacturer's instructions;
- transmit the DSC urgency call.
Transmission of the urgency message:
- tune the transmitter to the frequency or channel indicated in the DSC urgency call;
- transmit the urgency message as follows:
- "PAN PAN", repeated 3 times,
- "ALL STATIONS" or called station, repeated 3 times,
- "this is",
- the 9-digit identity and the call sign or other identification of own ship,
- the text of the urgency message.
Reception of an Urgency Message
Ships receiving a DSC urgency call announcing an urgency message addressed to all ships shall NOT acknowledge the receipt of the DSC call, but should tune the radiotelephony receiver to the frequency indicated in the call and listen to the urgency message.