Specialized Com Terms And Their Definitions

*Aeronautical telecommunication agency. An agency responsible for operating a station or stations in the aeronautical telecommunication service.

*Aeronautical telecommunication service. A telecommunica- tion service provided for any aeronautical purpose.

*Aeronautical telecommunication station. A station in the aeronautical telecommunication service.

*Aircraft operating agency. The person, organization or enterprise engaged in, or offering to engage in, an aircraft operation.

*Double channel simplex. Simplex using two frequency channels one in each direction.

Note.— This method was sometimes referred to as cross band.

*Duplex. A method in which telecommunication between two stations can take place in both directions simultaneously.

*Frequency channel. A continuous portion of the frequency spectrum appropriate for a transmission utilizing a specified class of emission.

*International telecommunication service. A telecommunica- tion service between offices or stations of different States, or between mobile stations which are not in the same State, or are subject to different States.

*Offset frequency simplex. A variation of single channel simplex wherein telecommunication between two stations is effected by using in each direction frequencies that are intentionally slightly different but contained within a portion of the spectrum allotted for the operation.

*Simplex. A method in which telecommunication between two stations takes place in one direction at a time.

Note.— In application to the aeronautical mobile service this method may be subdivided as follows:
a) single channel simplex; b) double channel simplex; c) offset frequency simplex.

*Single channel simplex. Simplex using the same frequency channel in each direction.

*Aeronautical fixed telecommunication network (AFTN). A worldwide system of aeronautical fixed circuits provided, s part of the aeronautical fixed service, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics.

*AFTN communication centre. An AFTN station whose primary function is the relay or retransmission of AFTN traffic from (or to) a number of other AFTN stations connected to it.

*AFTN destination station. An AFTN station to which messages are addressed for local delivery to the addressee.
AFTN entry-exit points. Centres through which AFTN traffic entering and leaving an ICAO Air Navigation Region should flow.

*AFTN group. Three or more radio stations in the aeronautical fixed telecommunications network exchanging communications on the same radio frequency.

*AFTN origin station. An AFTN station where messages are handed in for transmission over the AFTN.

*AFTN station. A station forming part of the aeronautical fixed telecommunication network (AFTN) and operating as such under the authority or control of a State.

*Automatic relay installation. A teletypewriter installation where automatic equipment is used to transfer messages from incoming to outgoing circuits.

Note.— This term covers both fully automatic and semi- automatic installations.

Channel. A single means of direct fixed service communication between two points.

Circuit. A communication system which includes all the direct AFTN channels between two points.

*Communication centre. An aeronautical fixed station which relays or retransmits telecommunication traffic from (or to) a number of other aeronautical fixed stations directly connected to it.

*Fully automatic relay installation. A teletypewriter instal- lation where interpretation of the relaying responsibility in respect of an incoming message and the resultant setting-up of the connections required to effect the appropriate retransmissions is carried out automatically, as well as all other normal operations of relay, thus obviating the need for operator intervention, except for supervisory purposes.

*Incoming circuit responsibility list. A list, for each incoming circuit of a communication centre, of the location indicators for which relay responsibilities are to be accepted in respect of messages arriving on that circuit.

*Location indicator. A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the location of an aeronautical fixed station.

Relay time. The relay time of a COM centre is the elapsed time between the instant that a message has been completely received at that centre and the instant that it has been completely retransmitted on an outgoing circuit.

Route (AFTN). The path followed by a particular channel of a circuit.

Routing (AFTN). The chosen itinerary to be followed by messages on the AFTN between acceptance and delivery.

*Routing Directory. A list in a communication centre indica- ting for each addressee the outgoing circuit to be used.

*Routing List. A list in a communication centre indicating for each addressee the outgoing circuit to be used.

*Semi-automatic relay installation. A teletypewriter installation where interpretation of the relaying responsibility in respect of an incoming message and the resultant setting-up of the connections required to effect the appropriate retransmissions require the intervention of an operator but where all other normal operations of relay are carried out automatically.

*“Torn-tape” relay installation. A teletypewriter installation where messages are received and relayed in teletypewriter tape form and where all operations of relay are performed as the result of operator intervention.

Transit time. The elapsed time between the instant of filing a message with an AFTN station for transmission on the network, and the instant that it is made available to the addressee.

*Tributary station. An aeronautical fixed station that may receive or transmit messages and/or digital data but which does not relay except for the purpose of serving similar stations connected through it to a communication centre.

*Aeronautical mobile service. A mobile service between aeronautical stations and aircraft stations, or between aircraft stations, in which survival craft stations may participate; emergency position-indicating radiobeacon stations may also participate in this service on designated distress and emergency frequencies.

*Aeronautical station. A land station in the aeronautical mobile service. In certain instances, an aeronautical station may be placed on board a ship or an earth satellite.

*Aircraft station. A mobile station in the aeronautical mobile service, other than a survival craft station, located on board an aircraft.

*Air-ground communication. Two-way communication between aircraft and stations or locations on the surface of the earth.

*Air-ground control radio station. An aeronautical telecommunication station having primary responsibility for handling communications pertaining to the operation and control of aircraft in a given area.

*Air-to-ground communication. One-way communication from aircraft to stations or locations on the surface of the earth.

*Alternative means of communication. A means of communication provided with equal status, and in addition to the primary means.
General purpose system (GP). Air-ground radiotelephony facilities providing for all categories of traffic listed in Categories of Com messages.

Note.— In this system communication is normally indirect, i.e. exchanged through the intermediary of a third person.

*Ground-to-air communication. One-way communication from stations or locations on the surface of the earth to aircraft.

*Non-network communications. Radiotelephony communi- cations conducted by a station of the aeronautical mobile service, other than those conducted as part of a radio- telephony network.

*Operational control communications. Communications required for the exercise of authority over the initiation, continuation, diversion or termination of a flight in the interest of the safety of the aircraft and the regularity and efficiency of a flight.

Note.— Such communications are normally required for the exchange of messages between aircraft and aircraft operating agencies.

“Pilot-controller” system. Air-ground radiotelephony facilities implemented primarily to provide a means of direct communication between pilots and controllers.

*Primary means of communication. The means of com- munication to be adopted normally by aircraft and ground stations as a first choice where alternative means of communication exists.

*Radiotelephony network. A group of radiotelephony aero- nautical stations which operate on and guard frequencies from the same family and which support each other in a defined manner to ensure maximum dependability of air- ground communications and dissemination of air-ground traffic.

*Regular station. A station selected from those forming an en- route air-ground radiotelephony network to communicate with or to intercept communications from aircraft in normal conditions.