第二章全部教案..

Distress, Urgency and Safety Communications
2.1 GMDSS GENERAL PROVISIONS总则
为了完善新系统，并且使新的遇险安全系统更为有效，当时制订了一系列新规章，当时主要体现在ITU“无线电规则”新九章的制订。

要求：GMDSS船舶，遵守ITU N IX
非GMDSS船舶，遵守ITU IX
规定了诸如：呼叫程序、频率、发射、调制的种类等等。

但是，涉及遇险时有例外情况。

【Global Maritime Distress and Safety System (GMDSS) was set up to provide an international communications network to assist vessels in distress. All distress communications in the maritime mobile service by radio tel ephony, d igital s elective c alling and satellite whether and/or direct printing telegraphy (telex), must be conducted strictly in accordance with the correct procedures. This ensures that vessels in distress obtain help without delay. Ships equipped for and operating under GMDSS conditions are obliged to comply with chapter N IX of the ITU Radio Regulations. Some provisions of this chapter also apply to the aeronautical mobile service except in the case of special arrangements
between the governments concerned. However, stations of the maritime mobile service when equipped to conform to chapter IX of the ITU Radio Regulations, shall comply with the provisions of that chapter.】
只要涉及到海上移动业务，N IX 即可生效：船对船
船对航空器
【The procedures specified in chapter N IX of the ITU Radio Regulations are obligatory in the maritime mobile satellite service and for communications between stations on board aircraft and stations of the maritime mobile satellite service, wherever this service or stations of this service are specifically mentioned.
The International Convention for the Safety of Life at Sea (SOLAS), 1974, prescribes which ships and which of their survival craft shall be provided with radio equipment, and which ships shall carry portable radio equipment for use in survival craft.
Although the procedures are obligatory for all stations using communications in the maritime mobile and maritime mobile satellite service they do allow:
(a) Mobile Earth Stations (MESs) in distress to use any means at their
disposal to attract attention, make known their position and obtain help;
(b) Any stations whether mobile (ship/aircraft) or land stations or coast
stations involved in search and rescue duties to use, in exceptional
circumstances, any means at their disposal to assist a mobile station or
a mobile earth station in distress;
(c) Any land (or coast station) or LES may use, in exceptional
circumstances, any means at their disposal to assist a mobile station or MES in distress.】
遇险报发送时的基本要求：
【When transmitting distress, urgency or safety messages by radiotelephony, transmissions should be made slowly and distinctly with clear pronunciation. The use of the I nternational C ode of S ignals is recommended, including the use of abbreviations and the phonetic alphabet, particularly in situations where language difficulties exist. Mobile stations may communicate with aircraft for safety purposes, but they must use the approved frequencies and observe the correct procedures. Aircraft which are required by national or international regulations to communicate with maritime mobile stations for safety purposes must comply with GMDSS provisions. Therefore until the full implementation of GMDSS, they must be able to transmit and receive:
(a)Class J3E emissions on carrier frequencies 2182kHz and 4125
kHz;
J3E：抑制载波的单边带电话
(b)Class G3E emissions on Channel 16 VHF and optionally Channel
6 VHF.
G3E：调频电话】
2.1.1 Distress frequencies
卫星系统
遇险频率
地面系统∨
为了保障遇险通信的可靠性，在ITU N IX中分配了一系列遇险和安全频率。

特点(地面系统)：
1）主要的呼叫方式：数字选择性呼叫技术。

2）主要的后续通信方式：电话、电传。

3）主要的工作方式：单工单频
【Within GMDSS a number of frequencies are specifically allocated for distress communication purposes depending on the communication medium being used. These frequencies should be used by ships, aircraft or survival craft when seeking assistance in the maritime mobile service. They should be used for the distress call and distress traffic and for calls preceded by either the urgency signal or the safety signal.】
DSC, radiotelephone and telex distress and safety frequencies are listed below.
4125KHZ：船和航空器之间的通信频率
The frequency 4125 kHz may be used by aircraft engaged in search and rescue (SAR) operations for distress/safety communications to stations in the maritime mobile service.
2182KHZ：船对船、船对航空器的遇险和安全频率；
兼作海事移动业务中的呼叫回答频率
2182 kHz is used as the international distress and safety frequency and also for international call and reply at the present time. However with the full implementation of GMDSS 2182 kHz is likely to be used exclusively for distress and safety purposes.
3023，5680KH：航空器电台和岸基电台的通信频率
The aeronautical frequencies 3023kHz and 5680kHz are used for intercommunication purposes between mobile stations and to participating land stations during coordinated SAR operations.
2.1.2 Aeronautical frequencies
航空器紧急频率：121.5MHz, 既是航空器的紧急甚高频无线电话频率，也是海事移动业务中卫星示位标频率之一。

2.1.3 GMDSS VHF Channel usage
Channel 6 VHF
1）搜救协调通信：船←→航空器
2）为了航行安全目的：船←→航空器
3）国内船舶：船舶之间的操纵、避让，中国沿海或有类似规定的沿岸航行时必须守听。

【Used for communication between ships and aircraft for coordinated SAR operations. May also be used by aircraft to communicate to ships for safety purposes.
Channel 13 VHF
国际航行船舶：船舶之间的操纵、避让
Used for ship to ship communication relating to safety of navigation. Channel 16 VHF
遇险和安全频率，兼顾呼叫与回答
Used for distress and safety traffic on RT, may also be used by aircraft for safety purposes.
Channel 70 VHF
ITU专门分配的VHF-DSC通信频率
Used as a DSC distress and safety calling channel in the maritime mobile service.】
2.1.4 Satellite service
卫星通信
1530—1544 Mhz 下行频率常规、遇险、安全通信
1544--1545 Mhz 下行频率遇险、安全通信
1626.5—1645.5Mhz行频率常规、遇险、安全通信
1645.5—1646.5Mhz上行频率遇险、安全通信
2.1.5 Survival craft 救生艇的相关频率
历史：GMDSS实施以前，救生艇电台以MORSE模式，工作在500KHz和RT模式工作在2182KHz。

Survival craft using equipment for emergency radio communication, location or alerting signals have to comply with certain conditions: TWO-WAY VHF：CH16和至少其他另外一个频率
【(a) Where portable VHF RT equipment operating in the allocated band (156-174 MHz) is used, it must be able to transmit and receive on Channel 16 and at least one other channel in this band.】
SART：9,200MHz----9,500MHz
【(b) Radar Search and Rescue Transponders (SARTs) transmitting locating signals must be able to operate in the frequency band 9200-9500 MHz (3 cm. or X-band).】
DSC: 甚高频波段CH70
高频8414.5MHz
中频2187.5MHz
【(c) Digital selective calling equipment if capable of operating on the indicated bands must be able to transmit on:
(i) 2187.5 kHz in the band 1605-2850 kHz;
(ii) 8414.5 kHz in the bands 4000-27500 kHz;
(iii) Channel 70 VHF in the band 156-174 MHz.】
2.1.6 Protection of distress frequencies频率的保护
【It is imperative（重要）that distress and safety communications maintain the best possible integrity and the distress and safety frequencies are protected from harmful interference, harmful interference being interference which puts at risk the operation of safety services or radio navigation services or seriously degrades, obstructs, or repeatedly interrupts any radio communication services. Therefore to protect distress integrity and to prevent harmful interference it is absolutely forbidden to broadcast or cause harmful interference by any emissions on any frequency especially those allocated to distress working.】
分析：伴随通信技术的发展，频道之间的距离允许设置得较小，从最初的0.05MHZ发展成为0.025MHZ，节省了大量的频率资源。

但是，为了保证遇险通信的有序进行，CH16信道上下未做扩展，设置为保护频道，即：156.800+0.025MHZ作为保护频道。

为进一步保护该信道，ITU的“N IX”决定，禁止在
156.800+（0.025X1.5）=156.7625~~~156.8375MHZ
2.1.7 Transmitter tests发射测试
【Test transmissions should only be made when absolutely necessary and be kept to a minimum to avoid harmful interference especially on the distress and safety frequencies. Whenever practicable, artificial aerials （假负载）should be used but where aerials do have to be used tests should be conducted on low power and coordinated with competent authorities. Testing on distress and safety calling frequencies should be avoided.Testing stations must always identify themselves and make it clear they are sending a test transmission. Before making a test operators should listen on the frequency to be used to ensure that no distress or safety communications are in progress.】
2.1.8 GMDSS watch keeping arrangements
GMDSS 的执守
2.1.9 Watch keeping: alert calls
Some HF coast stations offer a watch facility on the HF DSC safety frequencies for GMDSS sea areas A3 and A4 are
As per Regulation 12 of Chapter IV of the Amendments to the 1974 SOLAS Convention (concerning radio communications for GMDSS), every ship, while at sea, shall maintain a continuous watch:
(a) on DSC Channel 70 VHF, if the ship, in accordance with the requirements of regulation 7.1.2 (of the amendments to the 1974 SOLAS Convention), is fitted with a VHF radio installation;
(b) on the distress and safety DSC frequency of 2 187.5 kHz,if the
ship, in accordance with the requirements of regulation 9.1.2 or 10.1.3 (of the amendments to the 1974 SOLAS Convention), is fitted with an MF radio installation;
(c) on the distress and safety DSC frequencies of 2 187.5 kHz and 8 414.5 kHz and at least one of the other HF DSC frequencies (4207.5, 6312, 12577 or 16804.5 kHz), the frequency chosen will be appropriate to the ship's position and time of day, if the ship, in accordance with the requirements of regulation 10.2.2 or 11.1 (of the amendments to the 1974 SOLAS Convention), is fitted with an MF/HF radio installation. This watch may be kept by means of a scanning receiver;
(d) for satellite shore to ship distress alerts, if the ship, in accordance with the requirements of regulation 10. 1. 1 (of the amendments to the 1974 SOLAS Convention), is fitted with an INMARSAT MES.〗
2.1.10 Dedicated DSC watch keeping receiver
特点：
1）单频或多频守听
2）自动接收、存盘，产生生光报警
3）编发简单的报文，如遇险、紧急、安全、常规等形式
4) 可以在单个或多个频率上滚动发送报文：
重要概念：单频呼叫尝试、单频呼叫尝试
频率设置：
VHF CH70/156.525MHz，为强制接受频率。

MF 2187.5KHz（遇险、紧急、安全频率，是强制接收频率）+2177.0KHZ等（常规通信频率）。

HF 8414.5KHz（遇险、紧急、安全频率，是强制接收频率）+4M，6M，12M，16M（非强制接受遇险、紧急、安全频率）+4M，6M，8M，12M，16M，18M，22M, 25M（常规通信频率）。

【This is a scanning type of receiver which sequentially switches between 2187.5 kHz and 8414.5 kHz(两个强制接收的遇险、紧急、安全频率). The receiver is able to detect a special "dot pattern"（点阵）at a particular speed (100 baud) which is sent at the beginning of every DSC call. Should a distress alert be intercepted(截获) on any band the call will be processed and an audible alarm will sound. When the receiver is connected to an associated DSC controller the incoming call will be displayed. Some types of equipment may have an automatic printer fitted
to give a hard copy of any incoming calls. The equipment can be manually programmed to scan any of the other four remaining HF maritime DSC distress and safety calling frequencies as well as the two frequencies mentioned above. It performs this scanning operation within two seconds before repeating the operation.】
2.2 DISTRESS COMMUNICATIONS遇险通信
1）本节的主要内容：报警、确认、转发、强制静默及其解除；2）相关的课外内容
报警的各种方式及各相关单元的动作：
INMARSAT
EPIRB 卫星系统
MF/VHF 船→岸；船→船报警；
DSC
HF 以8414.5为主船→岸报警；
其他手段：无线电话，手机等
A．如果从卫星收到报警
1. 转发到RCC；
2. 以NA VTEX EGC 形式向海上转发
B．如果从地面系统收到报警——DSC
岸台： 1. 转发到RCC，由RCC确认；
2. 或岸台直接确认：VHF——马上确认；
MF/HF——推迟1~~2分45秒确认；
3. 然后，岸台或RCC向海上转发。

非遇难船舶：
A．如果直接从难船收到报警
1．守听相应的频率（CH16 2182 KHz）
2．MF/VHF上以RT形式确认，以免使难船DSC设备停止工作；如果3分钟无人确认，可以使用DSC确认，使难船DSC 停止工作，避免占用遇险频率时间过长；
3．HF上，可以3分钟之后转发。

B．如果收到岸台转发的报警
1．守听相应的RT信道；
2．RT 的形式确认；
C．如果收到其他船舶转发的报警（DSC）
操作的步骤同“A”
2.2.1 Distress & safety operational procedures
遇险报警的主要步骤
1. 前提：船长授权
2.报警：
使用卫星的绝对优先等级，在常规通信信道进行；
使用卫星的遇险信道进行；
使用地面系统的DSC在VHF，MF，HF波段进行。

【Services available for distress and safety communications are terrestrial radio communication in the MF, HF and VHF bands and
satellite Communication. Distress alerts are transmitted either:
(a) Via satellite with absolute priority using the general communication
channels; or
(b) Via satellite using exclusive distress and safety frequencies; or
(c) Using DSC on the appropriate distress and safety frequencies in the
MF, HF or VHF bands.
The authority of the master or person responsible for the ship, aircraft or other vehicle is required before a distress alert can be transmitted.
All stations receiving a DSC distress alert must immediately cease any transmission which may interfere with distress traffic. Stations must continue the watch until the distress alert has been acknowledged.】
2.2.2 Distress alerting
遇险报警
定义：当有一个移动单元（船、航空器或其他交通工具）或一个人处于紧迫危险且需要援助时，才可以发送。

卫星系统
主要方式：
地面系统
【A distress alert transmission implies that a mobile unit (ship, aircraft or other vehicle) or a person is in distress or imminent danger and requires immediate assistance.
A distress alert may be defined as:
(a) In the terrestrial radio communication bands:
digital selective call using the distress call format; or
(b) In the satellite service:
message using the distress format for relay through space stations.
The distress alert must include the identification of the station in distress and its position. Other information such as the nature of the distress and type of assistance required or anything else which may facilitate rescue may be included in the alert.
Ship to shore distress alerts are used to warn Rescue Coordination Centers (RCC) that a vessel is in distress. This alerting is routed via LES using satellite transmissions from MES or EPIRB. Alternatively, using the terrestrial service,alerts from ship stations or EPIRBs are made to coast stations. Ship to ship alerts to warn other vessels in the vicinity of the distressed vessel of the distress situation using DSC techniques in the MF and VHF terrestrial bands. The HF band may also be used.】
Shore to ship distress alert relay
岸对船的遇险转发
重要意义：标志着新的系统把报警重点由船对船转为船对岸，兼顾船对船的方式。

〖A coast station or an RCC which receives a distress alert shall initiate the transmission of a shore to ship distress alert relay. This distress alert relay will be addressed to all ships, to selected ships or to an individual
ship using the satellite or terrestrial service. Such alert relay messages must contain the identification of the mobile unit in distress, its position and any additional information which facilitates rescue operations.〗
Distress alert by a station not itself in distress
船台对遇险报文的转发
前提条件：遇难船舶没有能力发送遇险报文；
其他船舶认为有必要这样做。

重要意义：标志着新的系统继承了老系统中船舶互助的模式【Where a station in the mobile or mobile satellite service learns another mobile unit is in distress it must transmit a distress alert when:
(a) the mobile unit in distress is not in a position to transmit the distress
alert itself; or
(b) the master or person responsible for the mobile not in distress or the
person responsible for the land station considers further help is required.
A station transmitting a distress alert relay must make it very clear that it is not itself in distress.】
Acknowledgement of receipt of distress alerts
遇险报文的确认
定义：对于一份遇险报文的确认，应该首先得到船长的授权，它标志着有台站收到遇难船只发出的报文，表明收妥方收妥报文并将按规定的程序采取救助行动，即展开救援或将报文向相关的部门转发。

此时，遇难船只可以采取进一步的脱险措施。

1）岸站在卫星系统收到遇险报文，应该在卫星系统马上进行确认。

2）如果岸台在地面系统的DSC收到报警，应该：
VHF-DSC：马上使用DSC确认。

MF/HF-DSC：推迟1到2 ¾分钟，使难船DSC发信机完成一个多频呼叫尝试工作周期，然后使用DSC进行确认。

注意：应该遵循同频率的原则。

3）如果船台在地面系统的DSC收到报警，应该：
VHF-DSC：如果确认遇难船就在附近，并且在岸台覆盖范围以外，可以马上进行确认；否则推迟确认，让岸台首先使用DSC 确认。

MF：让岸台首先使用DSC确认，船台可以首先使用RT确认。

HF：守听3分钟，如果没人确认，船台只能转发。

注意：应该遵循同频段的原则。

重点内容：RT的确认格式
〖S atellite service
Acknowledgement of receipt of an alert from a MES must be sent immediately. Acknowledgement of receipt of a distress alert by DSC on terrestrial bands must be in accordance with relevant recommendations.
Radiotelephony
Acknowledgements from a ship or MES are given after the distress message has been received and must take the standard RT form:
●the distress signal MAYDAY;
●the call sign or other identification of the station sending the distress message,
spoken three times;
●the words THIS IS (or DE spoken as DELTA ECHO in the case of language
difficulties);
●the call sign or other identification of the station acknowledging receipt, spoken
three times;
●the word RECEIVED (or RRR spoken as ROMEO ROMEO ROME in the case
of language difficulties);
●the distress signal MAYDAY.
Example:
MAYDAY NONSUCH NONSUCH NONSUCH
THIS IS
SEASTAR SEASTAR SEASTAR
RECEIVED MAYDAY
radiotelex
knowledgements must be given in the form:
●the distress signal MAYDAY;
●the callsign or other identification of the station sending the distress
●alert;
●the word DE (meaning "this is" or "from"); the callsign or other identification of
the station acknowledging receipt of the distress alert;
●the signal RRR;
●the distress signal MAYDAY.
Example:
MAYDAY
BXXX DE BAAA
RRR MAYDAY
Acknowledging receipt of the distress alert from an MES using directing telegraphy is given by a LES receiving the alert by retransmitting the ship station identity of the MES sending the alert.〗
2.2.6 Acknowledging receipt of distress alerts by coast stations, LESs or RCCs
地面系统对遇险报文的确认
【Coast stations or a land earth stations, on reception of the initial distress must forward the alert to the appropriate RCC as soon as possible.
The alert must be acknowledged as soon as possible by a coast station or RCC via a coast station or appropriate LES.
Where a coast station uses DSC to acknowledge a distress alert the acknowledgement must be made on the same distress calling frequency used for the original alert and be addressed to all ships. Details of the identity of the ship in distress must be included in the acknowledgement message.】
2.2.7 Acknowledging receipt of distress alerts by ship stations or MESs
船台对遇险报文的确认
【A ship or MES receiving a distress alert must inform the master or person responsible for the ship of the contents of the alert as soon as possible.
In those areas where reliable communications with a coast station is possible, ships should delay acknowledgement for a short period to permit coast stations to acknowledge first. Ships may be trading in areas where reliable communication with a coast station is not practicable. In these
circumstances if they receive a distress alert from a ship station which is beyond doubt in their vicinity they must acknowledge receipt as soon as possible. They must also, if so equipped, inform a RCC of the alert via a coast station or LES.
Ships receiving an HF distress alert do not acknowledge it but should set watch on the RT frequency indicated in the distress alert, they may also set watch on the telex (NBDP) frequency associated with the distress alert frequency. If however the alert is not acknowledged by a coast station within three minutes then the receiving ship station must relay the distress alert.
Ships acknowledging receipt of a distress alert under the circumstances outlined above should:
(a) acknowledge receipt of the alert using RT on the distress and safety
frequency on the band used for the alert;
(b) acknowledge the alert using DSC on the appropriate frequency, if
acknowledgment by RT of an alert received on the MF or VHF distress alerting frequency is unsuccessful.
Ships which have received a shore to ship distress alert should establish communication as directed by the shore station and render assistance as required.】
2.2.8 Preparations for handling distress traffic
遇险通信的准备----同频段的原则
〖On receipt of a transmitted DSC distress alert, ship and coast stations must set a watch on the radiotelephone distress and safety frequency associated with the frequency on which the distress alert was received. For example, if the DSC distress alert was transmitted on 6312 kHz then a listening watch must be set on the RT distress frequency of 6215 kHz. Similarly ship and coast stations with NBDP equipment must set watch in the NBDP distress frequency if the distress alert message indicates that NBDP is to be used for subsequent communications. If practicable stations should set watch on the appropriate RT frequency associated with the distress alert frequency.〗
2.2.9 Distress traffic
遇险通信
〖The distress traffic is defined as all messages relating to the immediate assistance required by the ship in distress. It also includes search and rescue (SAR) communications and on-scene communications. All distress traffic should take place as far as possible on the frequencies set aside in band for this purpose.
When using radio telex for distress traffic, error correction techniques must be used. All messages must be preceded by at least one carriage return, a line feed signal, a letter shift signal and the distress signal MAYDAY. Distress communication should be established by the ship in
distress and should be made in the broadcast forward error correction mode. ARQ mode may subsequently be used where it is advantageous to do so.〗
2.2.10 Imposing silence强制静默
主要内容：在搜救过程中，RCC直接或指定某个搜救单元负责通信纪律。

如果在救助过程中，有电台对遇险通信产生干扰，RCC或指派电台有权强制该干扰电台静默，知道遇险通信结束。

强制静默标志符；SEELONCE MAYDAY→由RCC或指派的管制台；
SEELONCE DISTRESS→由非指派的台站发出〖The RCC responsible for controlling SAR operations also coordinates the distress traffic relating to the incident, it may however appoint another station to do this. Controlling stations may impose silence on stations which interfere with distress or SAR traffic; this may be addressed to all stations or to an individual station. The procedure used is:
(a)in radiotelephony, the signal SEELONCE MAYDAY,
pronounced as in the French expression "silence, m'aider";
(b)in NBDP telex normally using FEC mode the signal SILENCE
MAYDAY. However the ARQ mode may be used when it is advantageous to do so.
All stations which are aware of distress traffic but are not taking part in forbidden to transmit on the frequencies being used for distress
until they receive a signal indicating normal working may be resumed.
A station in the mobile service which is able to continue its normal while following distress traffic may do so. This is when the distress is well established and provided the mobile station does not interfere with distress traffic as previously indicated.〗
2.2.11 Resumption of normal working
正常通信的恢复
主要内容：遇险通信结束后，RCC或指定台站应该进行广播，指明。

标志符：SEELONCE FEENEE：遇险通信结束，正常通信恢复PRU-DONCE：遇险通信未结束，正常通信可适当恢复【When distress traffic has ceased on frequencies which have been used for distress traffic the RCC or station controlling SAR operations must initiate a message for transmission on those frequencies indicating the distress traffic has finished.】
On radiotelephony this message consists of:
●the distress signal MAYDAY;
●the call 'Hello all stations' or CQ (spoken as CHARLIE QUEBEC
spoken three times);
●the words THIS IS (or DE spoken as DELTA ECHO in the case
language difficulties);
●the call sign or other identification of the station sending the message
the time of handing in the message;
●the name and call sign of the mobile station which was in distress; the
words SEELONCE FEENEE pronounced as the French word “silence fini”.
Example:
MAYDAY
HELLO ALL STATIONS, ALL STATIONS, ALL STATIONS
THIS IS
SEASTAR SEASTAR SEASTAR,
0920 NONSUCH/BXXX SILENCE FINI
IN NBDP
Example:
MAYDAY
CQ DE BAAA
0920 NONSUCH/BXXX
SILENCE FINI 〗
2.2.12 On-scene communications
现场通信
【On-scene communications are those between the mobile unit in distress and assisting mobile units. It also includes communications between mobile units and the unit coordinating SAR operations, i.e. the on-scene commander (OSC) or the coordinator surface search(CSS). The OSC
or CSS has the responsibility of controlling the on-scene communications and selecting or designating the frequencies to be used for this purpose. The preferred frequencies for RT on-scene communication are 2182 kHz and channel 16 VHF,using simplex transmissions so that all on-scene mobiles share the relevant distress information.
NBDP telex frequency of 2174.5 kHz may also be used for ship to ship on-scene communications but if selected then forward error correction(FEC) mode must be used.
In addition to 2182 kHz and Channel 16 VHF, the frequencies listed may be used for on-scene communications between ships and aircraft. 3023 kHz.
4125 kHz.
5680 kHz.
channel 6 VHF.
Once an on-scene frequency has been established, a continuous aural or inter watch is maintained by all participating on-scene mobile units on that frequency.】
Mobile stations of the maritime mobile service may communicate with stations of the aeronautical service on the aeronautical emergency frequency 121.5 MHz for distress and urgency only, and on the aeronautical auxiliary frequency of 123.1 MHz for coordinated SAR operations, using class A3E emissions for both frequencies. They shall comply with any special arrangements between the governments
concerned by which the aeronautical mobile service is regulated.
2.2.13 Locating and homing signals
寻位信号
〖Locating signals are used to facilitate the finding of a mobile unit in distress or the location of survivors. Signals can be transmitted by:
(a) the mobile station in distress;
(b) survival craft;
寻位信号的发送 (c) satellite EPIRBs, or VHF EPIRBs ;
(d) search and rescue radar transponders (SART);
(e) units searching for the mobile in distress.
Locating signals may be transmitted in the following frequency bands.
117.975-136 MHz
寻位信号一般频段156-174 MHz (VHF)
406-406.1 MHz
9200-9500 MHz (X-band radar)
Homing signals are transmitted by mobile units in distress or by survival craft to provide searching units with a locating signal used to determine the bearing of the transmitting stations.〗
〖2.2.14 Search and rescue transponders (SARTS)
In GMDSS, SARTs are mandatory requirements and are used as homing devices to assist rescue craft locate the position of the distress incident.〗
2.2.15 Charging for distress communication
免、减费用的情况和各种特服号码及其功能
主要内容：
为了航运人员在特殊情况下毫不犹豫地使用INMARSAT系统，INMARSAT组织承诺，对于遇险、紧急、医疗指导等几种通信减或免除INMARSAT卫星的使用费用。

〖The INMARSAT council defined what constituted distress and safety calls and confirmed that calls conforming to these definitions would not be charged for the use of satellites. This took effect from 1 January 1992, a month before GMDSS was introduced. The definition of ship to shore distress and safety traffic is:
(a) distress alerts;
(b) SAR coordination communications including communication subsequent to the initial distress alerts, by voice or telex, relating to the immediate assistance required by a ship which is in distress and in grave and imminent danger, provided that they are made to associated rescue coordination centers via code 39;
(c)urgent navigational / meteorological danger reports by telecommunications via code 42;
(d) medical assistance for grave and imminent danger, by voice or telex
via code 38 to an agency recognized by national maritime administrations.
Equivalent（相等的）waiver（弃权）arrangements cover ship to shore traffic. It was also agreed that reduced charges will apply for ship to shore medical advice communications via code 32.〗
2.2.16 Distress communications by DSC
DSC的遇险通信
2.2.16.1 Alerting by DSC: general information
DSC的遇险报警
重要内容；多频呼叫尝试、单频呼叫尝试
〖DSC alerting equipment provides for automatic alerting without the need for aural watch and can operate under conditions of poor signal and high noise interference. Some DSC controllers automatically switch the transmitter to the correct DSC frequency (2187.5 kHz) when the distress condition is selected.
DSC controllers may be interfaced with electronic navigating equipment to update the ship's Position continuously. However where this facility is not connected, ships' navigating staff are recommended manually to enter the ship's position at regular intervals. This ensures that in the event of an emergency, recent positional information will be included in the distress alert.
Maritime Mobile Service Identity (MMSI). This is a nine digit DSC code which uniquely identifies the ship or coast station; it is permanently。