AFTN
(AERONAUTICAL FIXED TELECOMMUNICATION NETWORK)

AFTN Communication Centre.

Description of a typical AFTN COM Centre in late 70's like the Athens AFTN Com Centre.
A Semi Automatic store and forward Aeronautical messages switching centre, manifactured by Siemens. It was a heavy duty electromechanical machine with less electronics and much more relays and cables Hi Hi!
For an H24 service, five to six operators, per shift, were necessary to operate the Centre due to significant AFTN traffic exchanged, local and international. (Athens Com. Centre was designated as en entry-exit node for the international AFTN network for EUR , MID and AFI areas).
The composition of the operating positions was as follows:
One sypervisor position:
Duties: Responsible for the functionality of the centre by coordinating the operators and cooperating with the technical department. From the supervision console the sup operator had the ability to open or close incoming or outgoing channel, to bypass a channel, to divert the traffic in case of line saturation or intermediate memory saturation ,to accept or refuse additional tfc for qsp to edit and exchange service messages with the supervisors of associated com. centers, to send test messages (RY's) and finally to coordinate with the provider of the PTT lines in case of line failures or malfunctions.
Two "Routing" Positions (ES2):
Duties: Each operator had two screens where the incoming messages were displayed and the operator had to select from a keyboard the outgoing circuit(s) for transmission (according to a predefined responsibility table). If the message was corrupted the ES2 operator routed the message to the Monitor position for further action.
One "Routing" Position (ES1):
Duties: The operator had in his disposal three torn tape reading machines (Paper tape reader) and a keyboard from where he entered the outgoing circuits to route the messages originated locally. He had a visual contact with the supervisor's panel to route or not a message according to outgoing channels availability;
One torn tape preparation position:
Duties: Preparation of perforated paper tapes of all traffic issued locally like NOTAM Office and ATS. The perforated tape and the corresponing paper message were attached together and tranfered to ES1 position for transmition.
One monitor position:
Duties: The operator was responsible for visual monitoring for all the incoming traffic printed out on the teletype machines (each incoming channel had a dedicated teletype)
If a channel was "racing" , had interference or a message was corrupted he issued an appropriate service message (SVC) to the originator of the message or the previous aftn com centre to take action.
There were also as many teletypes as the outgoing channels (national and international). In those teletypes called FLM (First Line Monitor) were printed the address line , the origine line of the incoming message (the preable), the incoming channel from which the message was received, and the swithes (routings) made by the ES2 position. If a message was missrouted from the ES2 position or mal received from the remote station the operator issued the appropriate service message (QTA RPT, QTA MIS etc)
There was also a radio teletype equipement to monitor a wireless AFTN channel. Also the com centre included a separate radio room to exchange AFTN messages in CW mode, in case of PTT line failure or permanently with low traffic remote national aftn centres. In the same room the national NDB's were monitored by two dedicated LF receivers.
In the 90's the com. centre was already saturated and could not satisfy the demand for international aftn traffic relay, so Athens accepted messages mainly for LG area.
Finally end of 90's the Athens AFTN Com. centre replaced with a modern AFTN/CIDIN message swithing facility mady by SYSECA.

Examples of AFTN messages