1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 6 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$!4!G0G0#/-5.)#!4)/.G0G0/6%2G0G04(%G0G04%,%0(/.%.%47/2+).4%2#/%#4)/.G0G0“%47%.G0G005“,)#G0G0$!4!.%47/2+3G0G0 0$.SG9G0G0!.$G0G04(%G0G005“,)#37)4#(%$G0G04%,%0(/.%G0G0.%47/2+3G0G0 034.G9)45G134G0G0Recommendation
2、G0G06 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation V.100 was published in Fascicle VIII.1 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identic
3、al to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this
4、 publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VIII.1 - Rec. V.100 1Recommendation V.100Fascicle VIII.1 - Rec. V.100INTERCONNECTION BETWEEN PUBLIC DATA NETWORKS
5、(PDNs) AND THE PUBLIC SWITCHEDTELEPHONE NETWORKS (PSTN)(Malaga-Torremolinos, 1984)The CCITT,considering that(a) a data station may have an ingoing or outgoing access to a packet switched public data network (PSPDN)via the national1)PSTN;(b) the transmission characteristics of the data station may no
6、t be known at the PSPDN access level;(c) in this case, the transmission characteristics have to be negotiated between modems before establishingthe connection;(d) half-duplex modems as well as full duplex modems may be used;proposesthat Administrations may optionally introduce the following handshak
7、ing procedures including the types ofmodems to be supported.1 Procedure descriptionAccording to the type of modem (see Table 1/V.100), a half-duplex or a duplex procedure is used.1.1 Half-duplex procedureSee Figure 1/V.100.1.1.1 Answer mode modema) Following the transmission of the answer sequence i
8、n accordance with Recommendation V.25, themodem shall apply an ON condition to circuit 107, and then transmit a segment S1 in accordance withTable 1/V.100 for 294 ms. Interchange circuits 106 and 109 are in the OFF condition during theprocedure.b) The modem remains silent until it detects S2 (define
9、d in Table 1/V.100) or the synchronizing signals of aV.27 ter modem in the fallback mode.c) Then the modem conditions itself to the selected mode or disconnects.If no response is detected within 2 seconds following the end of the S1 transmission, the modem resumestransmitting S1._1)International acc
10、ess to a PSPDN via PSTN is not envisaged.2 Fascicle VIII.1 - Rec. V.100TABLE 1/V.100S2 and S1 signalsCategories Data rate(bit/s)Recommendation Procedure S2(calling DCE)S1(Answering DCE)Duplexasynchronous3001200V.21V.22DuplexDuplex980 Hz1200 Hz1650 Hz1800 + 2250 HzDuplexsynchronous(FDM)12002400V.22V.
11、22 bisDuplexDuplex1200 Hz1200 Hz1800 + 2250 Hz1800 + 2250 HzDuplexsynchronous(ECT)a)240048009600V.26 terV.32V.32Half-duplexDuplexDuplex(See V.26 ter)(See V.32)(See V.32)(See V.26 ter)(See V.32)(See V.32)Half-duplexsynchronous240048009600V.27 ter(fallback mode)V.27 ter(Under study)Half-duplexHalf-dup
12、lexHalf-duplexNone1400 Hz1100 HzNone2200 Hz2300 HzAsymmetricasynchronous75/1200 V.23 Duplex 390 Hz 1300 Hza)ECT = echo cancellation technique.Fascicle VIII.1 - Rec. V.100 3If S2 indicates a capability not available, the modem shall disconnect from the line.If S2 indicates a capability available, the
13、 modem conditions itself to this mode.d) After the end of reception of S2, in the case of a duplex modem (see V.26 ter), in accordance withRecommendation G.164, the modem transmits a 2100 15 Hz tone for 500 50 ms to disable echosuppressors, then remains silent for 75 20 ms.Note - In the case of half
14、-duplex modems, the transmission of the 2100 Hz tone is not needed.1.1.2 Call mode modema) After connection to line, the modem shall apply an ON condition to circuit 107 (interchange circuits 106and 109 are in the OFF condition during the procedure). The modem keeps silent during at least 400 ms.Dur
15、ing this period, it detects S1.The calling modem selects a mode of interworking in accordance with S1 or its nominal one.b) Then, it transmits S2 in accordance with Table 1/V.100 or the synchronizing signals of a V.27 ter modemin the fallback mode at 2400 bit/s.c) Then, it conditions itself to the s
16、elected capability.1.2 Duplex procedureSee Figure 2/V.100.4 Fascicle VIII.1 - Rec. V.1001.2.1 Answer mode modema) Following the transmission of the answer sequence in accordance with Recommendation V.25, themodem shall apply an ON condition to circuit 107 (interchange circuits 106 and 109 are in the
17、 OFFcondition during the procedure.b) Then, the modem transmits a segment S1 in accordance with Table 1/V.100 at least 40 10 ms and untilit has detected the end of transmission of S2.Note - During this period, some exchanges may occur between the two modems according to the Series VRecommendation co
18、ncerned (see Recommendation V.32).If no response is detected within a time period (under study), the modem shall disconnect from line.If S2 indicates a capability not available, the modem shall disconnect from the line.If S2 indicates a capability available, the modem conditions itself to this mode.
19、1.2.2 Call mode modema) In accordance with Recommendation V.25, after detection of the 2100 Hz tone and a silent period of75 20 ms, the modem shall apply an ON condition to circuit 107 (interchange circuits 106 and 109 arein the OFF condition during the procedure).b) The modem detects S1.The calling
20、 modem selects a mode of interworking in accordance with S1 or its nominal one.c) Then, it transmits S2 in accordance with Table 1/V.100.Note - If the modem has only one possibility, it may transmit S2 after being connected to line.d) Then, it conditions itself to the selected capability.2 Combined
21、half and duplex procedureThis section describes the interworking between a DCE having the capability of handling the two proceduresreferred to as two procedures (TP)modem and DCEs having only one procedure.2.1 Interworking with half-duplex procedure2.1.1 TP modem in the answering modeSee Figure 3/V.
22、100.Fascicle VIII.1 - Rec. V.100 52.1.1.1 Answer TP modema) After the V.25 sequence, the modem will transmit S1 which is composed of two segments S11 and S12(as described in Appendix I to Recommendation V.32).S11 is a modulated signal transmitted during 294 ms in a 600-3000 Hz bandwidth, S12 is a to
23、ne out ofthe 600-3000 Hz band.b) After the transmission of S12, the modem is waiting for S2. When it detects S2, it stops transmitting S12and proceeds with the half-duplex procedure.2.1.1.2 Calling modemThe calling modem shall proceed with the half-duplex procedure taking into account that S12 is an
24、 out-of-band signal.2.1.2 TP modem in the calling modeSee Figure 4/V.100.2.1.2.1 Answering modemThe answering modem shall proceed with the half-duplex procedure.2.1.2.2 Calling TP modemThe calling TP modem after the V.25 sequence and connection to line remains silent. It detects S1 and shallproceed
25、with the half-duplex procedure.2.2 Interworking with duplex procedure2.2.1 TP modem in the answering modeSee Figure 5/V.100.6 Fascicle VIII.1 - Rec. V.1002.2.1.1 Answering TP modemThe modem proceeds as in 2.1.1.1 except that after detection of S2, it shall follow the duplex procedure.2.2.1.2 Calling
26、 modemThe calling modem shall proceed with the duplex procedure.2.2.2 TP modem in the calling modeSee Figure 6/V.100.2.2.2.1 Answering modemThe answering modem shall proceed with the duplex procedure.2.2.2.2 Calling TP modemThe calling TP modem after the V.25 sequence and connection to line remains silent. It detects S1 and shallproceed with the duplex procedure.
