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such aircraft, and surface services, involved in common
search and rescue operations, prior to changing when 4.1.3.1.6 The emergency channel (121.5 MHz) shall be
necessary to the appropriate frequency; available only with the characteristics as contained in Annex 10,
Volume 111, Part 11, Chapter 2.
d) to provide air-ground communication with aircraft when
airborne equipment failure prevents the use of the
regular channels; 4.1.3.2 Air-to-air communications channel
e) to provide a channel for the operation of emergency
locator transmitters (ELTs), and for communication
between survival craft and aircraft engaged in search and
rescue operations;
f ) to provide a common VHF channel for communication
between civil aircraft and intercepting aircraft or
intercept control units and between civil or intercepting
aircraft and air traffic services units in the
event of interception of the civil aircraft.
Note I.- The use of the frequency 121.5 MHz for the
purpose outlined in c) is to be avoided if it interjeres in any
way with the eficient handling of distress traffic.
Note 2.- The current Radio Regulations make provisions
that the aeronautical emergency frequency 121.5 MHz may
also be used by mobile stations of the maritime mobile service,
using A3E emission to communicate on this frequency for
safety purposes with stations of the aeronautical mobile
service (RR S5.200 and Appendix S13, Part A2).
4.1.3.1.2 The frequency 121.5 MHz shall be provided at:
a) all area control centres and flight information centres;
4.1.3.2.1 An air-to-air VHF communications channel on
the frequency of 123.45 MHz shall be designated to enable
aircraft engaged in flights over remote and oceanic areas out of
range of VHF ground stations to exchange necessary
operational information and to facilitate the resolution of
operational problems.
Note.- Use of the air-to-air channel can cause interference
to and from aircraji using the same frequency for air-ground
communications.
4.1.3.2.2 In remote and oceanic areas out of range of
VHF ground stations, the air-to-air VHF communications
channel on the frequency 123.45 MHz shall be available only
with the characteristics as contained in Annex 10, Volume 111,
Part 11, Chapter 2.
4.1.3.3 Common signalling channel. The frequency
136.975 MHz is reserved on a worldwide basis to provide a
common signalling channel (CSC) to the VHF digital link
(VDL). This CSC uses the Mode 2 VDL modulation scheme
and camer sense multiple access (CSMA).
4.1.4 Auxiliary frequencies for search
and rescue operations
b) aerodrome control towers and approach control offices 4.1.4.1 Where a requirement is established for the use of a
serving international aerodromes and international alter- frequency auxiliary to 121.5 MH~a,s described in 4.1.3.1.1
nate aerodromes; and the frequency 123.1 MHz shall be used.
c) any additional location designated by the appropriate
ATS authority,
where the provision of that frequency is considered necessary
to ensure immediate reception of distress calls or to serve the
purposes specified in 4.1.3.1.1.
Note.- Where two or more of the above facilities are
collocated, provision of 121.5 MHz at one would meet the
requirement.
4.1.3.1.3 The frequency 121.5 MHz shall be available to
intercept control units where considered necessary for the
purpose specified in 4.1.3.1.1 f).
4.1.3.1.4 The emergency channel shall be guarded
continuously during the hours of service of the units at which
it is installed.
4.1.4.2. The auxiliary search and rescue channel
(123.1 MHz) shall be available only with the characteristics as
contained in Annex 10, Volume 111, Part 11, Chapter 2.
4.1.5 Provisions concerning the deployment
of VHF frequencies and the avoidance
of harmful interference
4.1.5.1 In the case of those VHF facilities providing
service up to the radio horizon, the geographical separation
between facilities working on the same frequency shall,
except where there is an operational requirement for the use
of common frequencies for groups of facilities, be such that
points at the protection heights and at the limit of the
functional service range of each facility are separated by
distances not less than that required to provide a desired to
undesired signal ratio of 14 dB. This provision shall be
Chapter 4 Annex 10 - Aeronautical Telecommunications
implemented on the basis of a regional air navigation agreement.
For areas where frequency assignment congestion is
not severe or is not anticipated to become severe, a 20 dB
(10 to 1 distance ratio) separation criteria or radio line-ofsight
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附件10--航空电信an10_v5_2ed(11)
