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TELEX -
the key to instant communication.


faq heading image

by Larry Rice


  1. What exactly is the telex network?
  2. How big is the telex Network and who uses it?
  3. Compare the differences between telex messages and facsimile messages.
  4. Technically, what happens when a telex message is sent?
  5. What are the abbreviations used on telex?
  6. How can one connect to the telex network and how much does it cost?
  7. Why would I use telex when I have facsimile or electronic mail?
  8. How did the telex network start?
  9. What's the difference between a telex machine and a teleprinter machine?
  10. What about sending a telex message say from England to Japan - will it be received in the Japanese language?


  1. What exactly is the telex network?

    The TELegraph EXchange Service is a 24 hour a day world-wide communications network.

    Customers communicate with each other by exchanging the typed word using CCITT International Telegraph Alphabet No.2 protocol.
    The communications session can be either be a real-time two-way keyboard-based conversation between 2 Telex subscribers or a simple straight forward typed message that has been prepared earlier offline for later automatic transmission.

    Telex is still the only form of transmission system which is legally recognized as possessing full legal document status.
    Governments use this medium extensively so they make sure that it is a reliable, up-to-date and well-maintained network.
    Telex offers the safeguard of the typed word.

    It is a reliable dedicated network that has stood the test of time and developed technologically for over 50 years.


  2. How big is the telex network and who uses it?

    There are approximately 1.7 million customers in over 200 countries.
    (400 in Australia).
    Users are from such fields as embassies and consulates, government departments, newspapers, airline offices, stock exchanges, business enterprises such as import/export agencies, hotels/motels, universities and many other diverse organisations.

    In 1996, British Telecom won a contract worth up to half a million Pounds to provide a telex-based charge card authorization service to American Express. Because of erratic telephone communications in Africa, American Express cards could not be used. But now by using telex, American Express can now give immediate authorization on all its card transactions and it now has a system which can be used from telex machines anywhere in the world including East European countries.
    (B.T. Today May 1996)

          Telex Network undergoing a revival. (B.T. Today April 2002)

    British Telecom's declining telex network is enjoying a new lease of life by becoming a means of delivering a low-cost and highly effective security service in conjunction with a data 300baud circuit.

    So successful is this usage of the telex network to provide the signalling medium that Lloyds Trustee Savings Bank has entrusted it for its property and panic alarm requirements across its sites and has increased its requirement to between 1,500 and 2,000 circuits.

    The UK dedicated telex network has been modernised so that this revitalised network incurs virtually no capital cost, whilst continuing to attract revenue.

    Allan Renton, head of telex support and engineering explains, "We supply the customer with an SS 300 circuit that is tied into the telex network and the customer purchases a modem and interface to hook up with the building monitoring panel. Once these are installed, the customer can use the network [with] whatever type of data they choose to send anywhere in the UK."
     


  3. Compare the differences between telex messages and facsimile messages.

    blue icon imageTLX: A secure, switched messaging service that conforms to international transmission standards. The telex network is used by government and business so the powers that be make sure this network works perfectly. Where the telephone systems do not perform well as in some countries in Africa, the telex network is maintained on a seperate telegraph network.
    red icon image FAX: Low line current on some telephone systems cause problems to facsimile transmission.

    blue icon imageTLX: A telex message consists of typed text using telex-compatible equipment either stand-alone or computer-based linked to a telex interface. The telex network is constantly being developed internationally using Intelligent Network technology.
    red icon imageFAX: A facsimile message has to be prepared beforehand. It can be typed, hand-written or contain graphics.

    blue icon imageTLX: Telex transmissions confirm and authenticate delivery from sender to receiver, and vice versa, through the exchange of strictly controlled answerback codes by the controlling telex administration. Telex directory enquiries can unpack the senders name and address from answerbacks, this means telex is one of the safest and most reliable ways for use as primary communications.
    red icon imageFAX: As it is the facsimile machine users responsibility to key in the Station ID, this can easily be changed or withheld, so the caller is never really sure that the message has reached the correct receiver. Horror stories are not unknown of 'secrets' being given away to foreign powers by careless or negligent checking of fax headers. Facsimile machines can easily be moved from one telephone line to another and not all users may be diligent to change the station ID accordingly.

    blue icon imageTLX: A telex message will often receive the same attention as a telegram/telemessage/lettergram, and will not usually remain unanswered for long.
    red icon imageFAX: In a pile of incoming facsimile messages, personal chit-chat messages can easily hide an important message.

    blue icon imageTLX: The sender of a telex message can be confident that the message will arrive perfectly at the distant end. Exchange of answerbacks after transmitting a telex message ensures that connection is still established with the distant end before the sender terminates the call.
    red icon imageFAX: Horizonal streaks with missing lines on received faxes are a result of a poor telephone connection or could be low line current from distant countries. Getting a repetition from far flung places could well be a chore. The writing implements some folk use to compile facsimile messages may make them hard to read at the distant end.

    blue icon imageTLX: Live keyboard two-way conversations can be had with the telex system.
    red icon imageFAX: Once the document has gone past the scanner and the wait time for more sheets has finished, the facsimile machine automatically clears down.


  4. Technically, what happens when a telex message is sent?

    Technology is changing the way the Telex system operates by taking the network off its own independent exchanges and 're-introducing' a similar VF system, that is, back to routing traffic via the phone network that was used on the Telex network way back in the 1930's. The only real difference is that different tones are used for send and receive instead of the simplex on/off tone 1500 cps method, and it's using modems with data compression protocol with additional equipment to interface the existing conventional telex network to co-exist upon the public switched telephone network. You can now send a telex message via the internet from a PC.

    In Australia, telex signalling is either double-current 50-0-50 by reversing a current that is normally on the line or FSK via the PSTN using FSK.
    Telex has two divisions of signalling, Type A and Type B.
    It's internationally agreed that if two countries with different types of signalling systems are trying to make a connection, the originating country will convert its outgoing signals to that of the receiving country.
    Type A signalling is where the keyboard is used to type in the called telex number.
    Type B signalling is where the telex dial is used to send the wanted telex number.
    Most countries have either changed or are in process of changing over to Type A keyboard selection as it's easier to incorporate into the intelligent systems used today.

    The telex equipment started with mechanical teleprinters, now the latest teleprinters are built around a microprocessor, disc drive, keyboard, VDU, printer together with word processor software to enable the operator to prepare, edit and store messages for later onward transmission. Telex computer software, telex forwarding services using Email-to-Telex, Real-Time conversational and store-and-forward via the Internet, all enhance the Telex network with the secure knowledge that you cannot unsuspectingly download a virus from a telex call.

    To initiate a telex call on a teleprinter using keyboard selection, the operator presses the call button and types in the wanted telex number finishing with a + (plus) sign. After a few secs either the wanted answerback code appears on the calling teleprinter/VDU screen or a service code is sent from the exchange. The operator checks that the answerback code is the desired one and signalling by ITA#2 5-unit code 5-unit code history can commence in either direction alternatively.

    Answerback codes consist of a pre-determined set of 20 characters signifying the telex number, customer name and the country of origin. International telex directories exist for unpacking answerback codes.
    Telex operates in simplex mode so both parties have a local record of what's being sent/received.


  5. What are the abbreviations/Service Codes used on telex?

    ABFF      Answerback Format faulty. red icon image
    ABS      Absent. (Office closed). red icon image
    ANUL      Delete.
    BK      I cut off.
    CFM      Confirm.
    CLG      Calling.
    COL      Collation please/I collate.
    CRV      How do you receive?/I receive well.
    DER      Dérangé. (Out of order) red icon image
    DF      You are in communication with the called telex service.
    GA      Go ahead/You may transmit.
    INF      Customer temporarily unobtainable.
    IFE      Office closed because of holiday.
    MNS      Minutes.
    MOM      Wait a moment please.
    MUT      Mutilation.
    N A      Correspondence to this international destination is not admitted.
    NA      Not Admitted. (Correspondence to this service is not admitted). red icon
image
    NC      No circuits. red icon image
    N C      No circuits (International).
    NCH      Number has been changed.
    NI      No line identification available.
    NP      No Plant. (The called number is not, or is no longer a telex service). red icon
image
    N P      The called international number has been typed incorrectly.
    NR      Indicate your number/My number is..
    OCC      Occupé. (Distant equipment occupied). red icon image
    PPPP      Stop transmission.
    PPR      Paper.
    R      Received.
    RAP      Rappel. (I shall call you back).
    RPT      Repeat/I repeat.
    SSSS      Here ready for data transmission.
    SVP      Sivousplait - Please.
    TAX      What is the charge/The charge is..
    TESTMSG      Please send a test message.
    THRU     You are now connected with a telex terminal.
    TPR     Teleprinter.
    W      Words.
    WRU Who are you?
    XXXXX Error.
    + +     End of transmission acknowledgement not required.
    +?     End of transmission, you may transmit.

    red icon image Service Codes, automatically generated by telex exchanges, are based upon a mixture of English and French expressions.


  6. How can one connect to the telex network and how much does it cost?

    A prospective customer would contact the telex network administration in their country and ask their advice on how to proceed. New and pre-owned equipment are likely to be available as well as a choice of computer-based equipment suppliers on the Internet.

    The costs of getting a dedicated telex line in Australia at time of writing are:
    $AU260.00 per annum for installation of new line.
    $AU37.00 per month plus call charges.
    Calls dialled automatically are charged in 6 second increments. International call rates depend on destination country from $AU1.46 per minute to $AU3.12 per minute.

  7.  


  8. Why should I use telex when I can use facsimile or electronic mail?
    (Assuming both parties have those systems)

    • Use Telex when you really need to make sure that important message has been well received by pressing the Bell key after transmission on a monitored call to get an on-line acknowledgement. The exchange of answerback codes anyway signify a good receipt. You may even get an immediate reply on the same connection. It is impossible to download a computer virus from the telex network.
      The shocking results of one study suggested that four out of every 10 e-mails sent to companies were being ignored.
    • Use Telex when legality of that transmitted message is needed.
    • Use Facsimile when images or handwriting need to be electronically transmitted.
    • Use Electronic Mail when no acknowledgement is needed that the email has been received by the addressee, notwithstanding mail unsent notifications from your internet provider.
    • When the addressee does not have any of the above services, and you do not wish to use the postal service, send a Telegram/Telemessage/Lettergram/Mailgram...etc.

  9. How did the Telex Network start?

    In U.K. June 1932, the "Telex Service", a switching service for teleprinter subscribers, was introduced for British Post Office administrative use followed by the opening to the public in London on 15th August 1932.
    Similar services were also commenced in several other European countries and in 1936 an international telex service, using 1500 cps signalling, was established between London and Amsterdam then onwards into the German telex network in 1937 and to a number of other countries.
    Germany inaugurated the worlds first automatic teleprinter exchange system, developed by Siemens and Halske, based on telegraph circuits in October 1933. Special modem equipment was installed in Amsterdam to accomodate the telephone to telegraph line conversion.
    The German automatic teleprinter exchange system was recognised world-wide as a most efficient system and received high acclaim. Over 90 percent of countries telex networks later adopted this model TW39 system. It was the CCITT Type B system with dial selection. Countries who opted for keying selection CCITT Type A system were initially very few, ie Australia, France, Italy, Netherlands, Norway.
    The first telex machines were connected to the telephone network alongside a telephone so by setting up a telephone call first, one then transferred that line to the teleprinter. It worked using a single-tone voice frequency carrier signal of 1500 cps which was keyed on and off by the teleprinter keyboard, a tone for a space element and no-tone for marking and idle periods. Telex subscribers had a basic modulator-demodulator (Modem) that was connected between their teleprinter and telephone line.
    Within a short space of time, the number of teleprinter subscribers increased to such an extent that it was more advantageous and economical to have an independent telegraph network both national and international. Conversion of the telex system to its own telegraph network in UK was completed in 1954. The bandwidth of a signal sent by telex is only about one twentieth the bandwidth of a telephone signal.
    Initially the networks were switched by manual exchanges but due to the popularity of telex by the business community, these were eventually upgraded to automatic exchanges.
    By 1956, telex service internationally was available to most of Europe, to Africa via radio links, to U.S.A. and Canada via voice frequency telegraph channels along the trans-atlantic telephone cable.
    Now, intelligent network technology such as *InTelex* has reverted the network back to using telephone lines in majority of countries using keyboard selection incorporating modems between the telex line at the subscribers end and, either the teleprinter, or the telex interface and the PC.


  10. What's the difference between a telex machine and a teleprinter machine?

    • A Telex machine is a teleprinter used on the telex network.
    • A Telex message is the communication transmitted/received on the telex network.
    • "A Telex" usually means a message sent on the telex network.
    • A Teleprinter is a device for transmitting and receiving the typed word using International Telegraph Alphabet No.2 code designed for start-stop telegraph systems.
    • A Teletype is a teleprinter manufactured by the Teletype Corporation.
    • A Creed is a teleprinter manufactured by the ITT-Creed Company.


  11. What about sending a telex message say from England to Japan - will it be received in the Japanese language?

    No. Japan's international telex carrier is KDD which uses normal 5-unit signalling, NTT is the domestic Telex carrier which uses 6-unit signalling for the Japanese script and is linked with KDD via signal converters for 6 to 5 unit and conversely 5 to 6 unit.
    In the United Arab Emirates, ETISALAT is supplying dual language telex machines capable of sending and receiving messages in both Arabic and Latin script. Telex subscribers in the UAE using the dual language machines can switch between Latin to Arabic or vice versa any number of times and it's possible to send the Arabic and Latin translations of the same message in the same transmission, assuming both parties have dual language machines. Telexing to the UAE from outside that country are assured that if a Latin answer-back is received back from the distant end, the called party can receive Latin script, and if the first symbol in that answer-back is an equals sign (=), it denotes that machine is a dual language machine.
    Telex users who have accented letters in their language on their teleprinter keyboards are advised not to use those letters internationally.



                            Rev: 15th March 2005