INTERNATIONAL TELECOMMUNICATION UNION
V.8
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
(11/2000)
SERIES V: DATA COMMUNICATION OVER THE
TELEPHONE NETWORK
General
Procedures for starting sessions of data
transmission over the public switched
telephone network
ITU-T Recommendation V.8
(Formerly CCITT Recommendation)
ITU-T V-SERIES RECOMMENDATIONS
DATA COMMUNICATION OVER THE TELEPHONE NETWORK
General V.1–V.9
Interfaces and voiceband modems V.10–V.34
Wideband modems V.35–V.39
Error control V.40–V.49
Transmission quality and maintenance V.50–V.59
Simultaneous transmission of data and other signals V.60–V.99
Interworking with other networks V.100–V.199
Interface layer specifications for data communication V.200–V.249
Control procedures V.250–V.299
Modems on digital circuits V.300–V.399
For further details, please refer to the list of ITU-T Recommendations.
ITU-T V.8 (11/2000) i
ITU-T Recommendation V.8
Procedures for starting sessions of data transmission
over the public switched telephone network
Summary
This Recommendation defines signals to be exchanged between DCEs over the PSTN when a
session of data transmission needs to be established, but before signals are exchanged which are
specific to a particular Recommendation. It provides means to automatically determine the best
available operational mode between two DCEs connected via the PSTN, provides a timely indication
to Circuit Multiplication Equipments on the V-series modulation to be employed in a new session of
data transmission, provides a means to enable a PSTN call to be passed on automatically to an
appropriate DCE, and provides signals for interacting with PSTN echo-control equipment.
This Recommendation was revised in 1998 and 1999 to define additional call function types, define
procedures for the exchange of non-standard facilities information and add support for PCM
modulation modes.
This Recommendation was revised in 2000 to provide support for V.92 features, correct errors in the
1999 version, clarify the use of the prot0 octet, and add clause 10 to address compatibility with
future revisions of this Recommendation.
Source
ITU-T Recommendation V.8 was revised by ITU-T Study Group 16 (2001-2004) and approved
under the WTSA Resolution 1 procedure on 17 November 2000.
ii ITU-T V.8 (11/2000)
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations
on them with a view to standardizing telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these
topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.
NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementors are
cautioned that this may not represent the latest information and are therefore strongly urged to consult the
TSB patent database.
ã ITU 2001
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU.
ITU-T V.8 (11/2000) iii
CONTENTS
Page
1 Scope........................................................................................................................... 1
2 References................................................................................................................... 1
3 Definitions .................................................................................................................. 3
4 Overview of the Recommendation ............................................................................. 3
4.1 Call indication............................................................................................................. 3
4.2 Call menu/Joint menu exchange ................................................................................. 3
5 Coding format ............................................................................................................. 4
5.1 Category octets............................................................................................................ 4
5.2 Extension octets .......................................................................................................... 4
6 Code tables.................................................................................................................. 4
6.1 Call functions.............................................................................................................. 5
6.2 Modulation modes ...................................................................................................... 6
6.3 PCM Modem availability............................................................................................ 7
6.4 Protocols ..................................................................................................................... 7
6.5 PSTN access ............................................................................................................... 8
6.6 Non-standard facilities................................................................................................ 8
7 Descriptions of signals................................................................................................ 9
7.1 Function indicator signal CI........................................................................................ 9
7.2 Modified answer tone ANSam.................................................................................... 9
7.3 The Call Menu signal CM .......................................................................................... 9
7.4 The Joint Menu signal JM .......................................................................................... 10
8 Data session start-up procedure .................................................................................. 11
8.1 Start-up procedure in the call DCE............................................................................. 11
8.1.1 Call signal transmission................................................................................. 11
8.1.2 Call menu transmission ................................................................................. 12
8.2 Start-up procedure in the answer DCE ....................................................................... 12
8.2.1 ANS transmission.......................................................................................... 12
8.2.2 ANSam transmission ..................................................................................... 12
8.2.3 JM transmission............................................................................................. 12
9 DTE-DCE interchange circuits ................................................................................... 13
10 Compatibility .............................................................................................................. 13
