џWPCL ћџ2BJ|xа АH аа АА X агга ХА6p&А6p&Х аеЅ† а Hh аааУ Уб cмˆ4 PŽТ б Fascicle VII.2 Р-Р Suppl. No. 1 PAGE1 Ѕе傆 а HH аааУ Уб cмˆ4 PŽТ бPAGE2 Fascicle VII.2 Р-Р Suppl. No. 1 ‚еа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X  аб cмˆ4 PŽТ бTHE DRAWINGS CONTAINED IN THIS SUPPLEMENT HAVE BEEN DONE IN AUTOCAD. ‚У УSupplement No. 1 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8<Сб cмˆ4 PŽТ бSIGNALLING CHARACTERISTICS AND TIMING OF THE Ср8HСMARISAT TELEX SERVICE аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8JСб cмˆ4 PŽТ бФ Ф(УУSource:ФФ COMSAT) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHјP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаУ У1ТX ТIntroductionФ ФЦЦ а Hh ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СIn response to Recommendation U.4, this Supplement describes the characteristics and time sequences of the international telex service operated over the MARISAT maritime satellite communication system. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У2С  СShip terminal originatedб cмˆ4 PŽТ б telex callЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СFigure 1 shows the signalling sequence for a telex call originated from a ship terminal in the MARISAT system. Figure 2 illustrates the telex signalling and timing sequence. The following is a general description of the sequence of events in establishing a telex call from a ship terminal to a gateway switch. а H а2.1С  СTo initiate a call, the ship terminal sends a telex request message in theУУ outР-РofР-РbandФФ request channel. The coast earth station receiving the valid request message will send back anУУ outР-РofР-РbandФФ assignment message instructing the ship terminal equipment to tune to the assigned channel. а H а2.2С  СOn the receipt of a validУУ outР-РofР-РbandФФ assignment message from the coast earth station, the ship terminal can then access its assigned channel. The terminal will normally achieve carrier and bit timing synchronization within 0.58 seconds after receipt of the assignment message. This time includes assignment message decoding, carrier recovery and clock recovery. Transmission will normally start upon frame synchronization, which occurs in less than 5.25 seconds. Therefore, the normal ship terminal response time will be less than 5.8 seconds as seen at the ship or 6.6 seconds as seen at the coast earth station. The time that the assignment message remains active in the coast earth station is in addition to this 6.6 seconds, allowing enough time for the ship terminal to start transmitting. 2.3С  СThe coast earth station, which is continually transmitting a spacing signal, makes the transition space to mark indicating call confirmation within one character (150 milliseconds not counting framing delays) after the assignement message is formatted. In cases of heavy traffic, the assignment message may be delayed in queue until after the transition has occurred, i.e., it is possible for the space to mark transition to be received by the ship terminal before the assignment message. а H а2.4С  СThe initial ship terminal transmission is in the spacing state. When a mark is received from the coast earth station, the terminal changes its transmission from space to mark. In the case when the space to mark transition on the coast earth station to ship terminal link reaches the terminal before the assignement message, the terminal inserts no more than two space characters in the initial burst. а H а2.5С  СOnce the coast earth station has received the terminal's space to mark transition, it sends a WRU (figure case D) to the ship terminal. The coast earth station must receive a 20 character answerback within 7 seconds from the end of the WRU character sequence or it will clear the call. In addition, the coast earth station sends aУУ request not acceptableФФ assignment message (outР-РofР-Рband) back to the terminal. The coast earth station does not check if the answerback code corresponds to the ship terminal's destination code (ID). 2.6С  СThe received answerback is stored by the coast earth station. Call processing is now started between the coast earth station and the gateway switch. The coast earth station presents a mark to the gateway switch and the gateway responds with aУУ call confirmationФФ within 1 second. Within 3 seconds after theУУ call confirmationФФ, the gateway returns aУУ call connectФФ. The coast earth station then connects the gateway switch to the ship terminal. The gateway then sends its header (if any) and a WRU to the ship terminal. After transmission of these signals, the coast earth station disconnects the circuit and sends the ship's answerback in storage to the gateway switch within 850 milliseconds. The ship terminal will send an answerback in response to the WRU from the gateway switch. However, this second answerback is blocked by the coast earth station. The coast earth station will connect the circuit after the 19th character of the ship's answerback is received, and the ship terminal can then send selection digits to the gateway switch. а H а2.7С  СAfter this second connection, the coast earth station does not respond to any data on the line until it detects clearing. а H а2.8С  СThe gateway switch, upon receipt of the selection sequence from the ship terminal, proceeds to process the call to the desired terrestrial subscriber. As the MARISAT system interfaces with various gateway switches, the signalling sequences proceed according to the protocol between the particular gateway switch and the terrestrial network. С СУУNoteФФ Р-Р The signalling sequences shown between the gateway switch and terrestrial network in Figure 1 illustrates one method of signalling which can be employed. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У3С  Сб cмˆ4 PŽТ бTelex call originated by a coast earth stationЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф3.1С  СFigures 3 and 4 illustrate the telex signalling and timing sequences for a telex call originated in a terrestrial network to a ship terminal via the MARISAT system. As the signalling sequences between the terrestrial networks and each gateway switch are not identical, that portion of the signalling sequences in Figure 3 are for illustrative purposes only and no attempt is made to describe all the possible sequences. а H а3.2С  СThe following paragraphs provide a description of the sequence of events which occurs between a gateway switch and a ship terminal for a telex call originated by a coast earth station. а H а3.2.1С СUpon receit of the selection digits from the terrestrial network, the gateway switch starts the signalling sequence by sending aУУ call requestФФ signal on an idle circuit to the coast earth station. Upon receipt, the coast earth station returns both aУУ call confirmationФФ andУУ proceedР-РtoР-РselectФФ signal within the proper intervals as shown in Figure 4. The gateway switch can then proceed to send the selection digits to the coast earth station. а H а3.2.2С СThe coast earth station checks the validity of the selection digits and if correct, sends anУУ outР-РofР-РbandФФ assignment message to the ship terminal requested. When the assignment message has been transmitted, the signalling proceeds in the same manner as a call from a ship terminal to a coast earth station described in РSР 2. Once the ship has accessed its assigned channel, the coast earth station sends a WRU to the ship terminal. The terminal responds with its answerback which is stored by the coast earth station. 3.2.3С СWhen the answerback is stored, the coast earth station sends aУУ call connectФФ signal to the gateway switch. The gateway then sends a WRU and its header toward the coast earth station. These signals are blocked at the coast earth station and prevented from going to the ship terminal. The coast earth station responds to the gateway's WRU with the ship terminal answerback it had previously stored. The coast earth station then interconnects the circuit between the gateway switch and the ship terminal. From this point, the coast earth station is essentially transparent to all data on the line until it detects aУУ clearingФФ signal. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У4С  Сб cмˆ4 PŽТ бTelex clearing sequenceЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф4.1С  СThe coast earth station recognizes aУУ clearingФФ signal as a spacing condition of 400 to 1000 milliseconds from either the gateway switch or a ship terminal. After recognition of theУУ clearingФФ signal, the coast earth station will disconnect the circuit and send aУУ clear confirmationФФ signal in both directions. а H а4.2С  СRelease of the satellite circuit section is under the control of the coast earth station. The ship terminal does not stop transmission of its RF carrier until; а H аТа ТТ№ ТС€ Сa)СpСit has returned aУУ clear confirmationФФ signal following the receipt of aУУд k+д clearingФФ signal from the coast earth station; orЦЦ а H аТа ТТ№ ТС€ Сb)СpСaУУ clear confirmationФФ signal is received from the coast earth station. In either case, the ship terminal maintains a spacing signal for a maximum of 3.09 seconds before transmission is terminated.ЦЦ а H а4.3С  СFor 6 seconds after the successful receipt of theУУ clearingФФ andУУ clear confirmationФФ signals over a circuit section between the coast earth station and a gateway switch, the coast earth station will not process any calls on that circuit section. The ship terminal is also considered busy during this 6Р-Рsecond interval. This 6Р-Рsecond guard time is necessary to allow for proper clearing of the ship terminal over the satellite circuit section. If another telex call is received for that ship terminal during the 6Р-Рsecond guard time, the coast earth station will send back anУ У OCCФ Ф service signal. ‚Ср JСб cмˆ4 PŽТ бFigure 1/suppl. 1 Љ CCITT 48390 б cмˆ4 PŽТ б Ср JСб cмˆ4 PŽТ бFigure 2/suppl. 1 Љ CCITT 48400 б cмˆ4 PŽТ б Ср JСб cмˆ4 PŽТ бFigure 3/suppl. 1 Љ CCITT 48410 б cмˆ4 PŽТ б Ср JСб cмˆ4 PŽТ бFigure 4/suppl. 1 Љ CCITT 48420 б cмˆ4 PŽТ б