SIST ETS 300 002 E1:2003

SLOVENSKI STANDARD
01-december-2003
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Y3671
Public Switched Telephone Network (PSTN); Category II attachment requirements for 9
600 or 4 800 bits per second duplex modems standardised for use on the PSTN
(Candidate NET 25)
Ta slovenski standard je istoveten z: ETS 300 002 Edition 1
ICS:
33.040.35 Telefonska omrežja Telephone networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 002
TELECOMMUNICATION February 1992
STANDARD
Source: ETSI TC-TE Reference: T/TE 04-09
ICS:
PSTN, Modems
Key words:
Public Switched Telephone Network (PSTN);
Category II attachment requirements for 9600 or 4800 bits per
second duplex modems standardised for use on the PSTN
(Candidate NET 25)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1992. All rights reserved.
New presentation - see History box

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ETS 300 002: February 1992
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Standards Approval Dept." at the address shown on the title page.

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ETS 300 002: February 1992
Contents
Foreword.7
1 Scope .9
2 Normative references .9
3 Definitions and abbreviations.9
3.1 Definitions.9
3.2 Abbreviations. 11
4 General requirements . 11
4.1 References to other ETSs . 11
4.2 Information to be provided by the applicant . 11
4.2.1 Information required for testing purposes . 11
4.2.2 Instructions for use. 11
5 Functional requirements specific to Category II modems . 12
5.1 General requirements. 12
5.2 Modes of operation/use. 12
5.3 Line signals. 13
5.3.1 Transmitted carrier frequency. 13
5.3.2 Receiver carrier tolerance. 13
5.3.3 Transmitted spectrum. 13
5.4 Line signalling rates. 14
5.5 Encoding of data. 14
5.6 Scrambler and descrambler. 14
5.7 Channel allocation . 14
5.7.1 Channel selection . 14
5.7.2 Automatic channel selection . 14
5.8 Hand-shaking sequences . 15
5.8.1 Definitions. 15
5.8.2 Auto-calling and auto-answering procedures. 17
5.8.2.1 Auto-calling - calling tone. 17
5.8.2.2 Auto-calling - recognition of answering tone . 17
5.8.2.3 Auto-answering . 17
5.8.3 Start-up procedure . 17
5.8.3.1 Call Mode Modem (CMM). 17
5.8.3.1.1 AA signal. 17
5.8.3.1.2 Round trip delay determination . 17
5.8.3.1.3 Rate negotiation. 18
5.8.3.1.4 Completion of the rate negotiation . 18
5.8.3.1.5 Completion of the hand-shake . 18
5.8.3.2 Answer Mode Modem (AMM). 18
5.8.3.2.1 Transmission of answer tone. 18
5.8.3.2.2 Round trip delay determination . 19
5.8.3.2.3 Rate negotiation. 19
5.8.3.2.4 Completion of rate negotiation. 19
5.8.3.2.5 Completion of the hand-shake . 20
5.8.4 Retrain sequence . 20
5.8.4.1 Initiating signal. 20
5.8.4.1.1 Call Mode Modem (CMM). 20
5.8.4.1.2 Answer Mode Modem (AMM) . 20
5.8.4.2 Response signal . 20
5.8.4.2.1 Call Mode Modem (CMM). 21

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ETS 300 002: February 1992
5.8.4.2.2 Answer Mode Modem (AMM) .21
5.9 Transmission of start-stop characters.21
5.10 Threshold of received line signal detector.21
5.11 Test loop 2 .21
5.11.1 Definitions.22
5.11.2 Instigation of a remote loop 2 .22
5.11.3 Termination of a remote loop 2.22
5.12 Receiver performance .23
5.12.1 Normal case.23
5.12.2 Case with satellite delay .23
Annex A (normative): Testing methods .24
A.1 General testing conditions.24
A.1.1 General notes .24
A.1.1.1 Test set-up . 24
A.1.1.2 Determination of signals.24
A.1.2 Limitation of number of tests .25
A.1.2.1 Introduction.25
A.1.2.2 General rules . 25
A.1.2.3 Specific rules .25
A.1.3 Proposed order for performing the tests .26
A.2 Test for subclause 5.3.1 (Transmitted carrier frequency).27
A.3 Test for subclause 5.3.2 (Receiver carrier tolerance) . 27
A.4 Test for subclause 5.4 (Line signalling rates) .27
A.5 Test for subclause 5.5 (Encoding of data) .27
A.6 Test for subclause 5.6 (scrambler and descrambler).28
A.7 Test for subclause 5.7 (Channel allocation).28
A.8 Test for subclause 5.8 (Hand-shaking sequences).28
A.8.1 Test for subclause 5.8.2 (Auto-calling and answering procedures) .28
A.8.1.1 Test for subclause 5.8.2.1 (Auto-calling - calling tone).28
A.8.1.2 Test for subclause 5.8.2.2 (Auto-calling - recognition of answering tone) .28
A.8.1.3 Test for subclause 5.8.2.3 (Auto-answering).28
A.8.2 Tests for subclause 5.8.3 (Start-up procedure).29
A.8.2.1 Tests for subclause 5.8.3.1 (CMM).29
A.8.2.1.1 Test for subclause 5.8.3.1.1 (AA signal).29
A.8.2.1.2 Test for clause 5.8.3.1.2 (Round trip delay determination) . 29
A.8.2.1.3 Test for subclause 5.8.3.1.3 (Rate negotiation).29
A.8.2.1.4 Test for subclause 5.8.3.1.4 (Completion of rate
negotiation) .30
A.8.2.1.5 Test for subclause 5.8.3.1.5 (Completion of the hand-
shake) .30
A.8.2.2 Tests for subclause 5.8.3.2 (AMM).31
A.8.2.2.1 Test for subclause 5.8.3.2.1 (Transmission of answer
tone).31
A.8.2.2.2 Test for subclause 5.8.3.2.2 (Round trip delay
determination) .32
A.8.2.2.3 Test for subclause 5.8.3.2.3 (Rate negotiation).32
A.8.2.2.4 Test for subclause 5.8.3.2.4 (Completion of rate
negotiation) .32
A.8.2.2.5 Test for subclause 5.8.3.2.5 (Completion of the hand-
shake) .33
A.8.3 Tests for subclause 5.8.4 (Retrain sequence).34

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ETS 300 002: February 1992
A.8.3.1 Tests for subclause 5.8.4.1 (Initiating signal) . 34
A.8.3.1.1 Tests for subclause 5.8.4.1.1 (CMM). 34
A.8.3.1.2 Tests for subclause 5.8.4.1.2 (AMM) . 34
A.8.3.2 Tests for subclause 5.8.4.2 (Response Signal). 34
A.8.3.2.1 Tests for subclause 5.8.4.2.1 (CMM). 34
A.8.3.2.2 Tests for subclause 5.8.4.2.2 (AMM) . 34
A.9 Test for subclause 5.9 (Transmission of start-stop characters) . 35
A.10 Tests for sublause 5.11 (Test loop 2) . 35
A.10.1 Tests for subclause 5.11.2 (Instigation of a Remote loop 2) . 35
A.10.1.1 Transmission of the test loop initiation signal - Test for subclause
5.11.2(a) (Controlling modem under test). 35
A.10.1.2 Response to the test loop initiation signal (Test for subclause 5.11.2(b))
(Controlled modem under test) . 35
A.10.2 Tests for subclause 5.11.3 (Termination of a remote test loop 2). 35
A.10.2.1 Transmission of the de-activation signal (Test for subclause 5.11.3(a))
(Controlling modem) . 35
A.10.2.2 Response to the de-activation signal (Test for subclause 5.11.3(b))
(Controlled modem). 36
Annex B (informative): Example proforma for the declaration of modes of operation/use. 37
Annex C (informative): Formal description of the start-up sequence. 40
Annex D (informative): Bibliography. 58
History. 59

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ETS 300 002: February 1992
Foreword
This European Telecommunications Standard (ETS) has been produced by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI). The text of this ETS
may be utilized, wholly or in part, for the establishment of NET 25.
This ETS contains the technical requirements for approval to Category II of 9600 or 4800 bits per second
duplex modems standardised for use on the Public Switched Telephone Network (PSTN). Testing and
approval to Category II is applicable only at the request of the applicant. These requirements are based
upon, and do not conflict with, CCITT Recommendation V.32 [3] (9600 bits per second duplex modem
standardised for use on the General Switched Telephone Network, 1988).
Additionally, requirements are included relating to end-to-end interoperability over PSTN connections. Such
requirements are in excess of the CCITT Recommendations.
Except where otherwise indicated a modem which complies with CCITT Recommendation V.32 [3] should
always meet the requirements of this ETS which relate to parameters specified in that CCITT
Recommendation.
Clause 4 of this ETS references the requirements common to both Category I and Category II modems,
which are contained in Clause 4 of ETS 300 114 [2]. The definitions for Category I and Category II
modems can be found in the foreword of ETS 300 114 [2].
Clause 5 of this ETS contains Category II requirements specific to 9600 or 4800 bits per second duplex
modems. In the case of certain functions common to a number of different types of modem (e.g. Auto-
answering sequence) reference is made to Clause 5 of ETS 300 114 [2], which contains the relevant
requirements.
Every ETS prepared by ETSI is a voluntary standard. This ETS has been prepared as a candidate NET
which may be transposed, in whole or in part, into a mandatory NET by the Technical Recommendations
Application Committee (TRAC). It therefore contains text concerning type approval of the equipment to
which it relates. This text should be considered only as a guidance and does not make this ETS
mandatory.
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ETS 300 002: February 1992
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ETS 300 002: February 1992
1 Scope
This ETS specifies the technical characteristics to be met by modems seeking Category II approval for
duplex operation over the PSTN at 9600 or 4800 bits per second. The modulation scheme specified is that
described in CCITT Recommendation V.32 [3].
The term "modem" in the context of this ETS includes all physical implementation practices for a voice
band modem, which are galvanically connected to the PSTN.
This ETS specifies six modes of operation, each with five modes of use (see subclause 5.2).
This ETS also contains descriptions of the tests to be performed in order to confirm compliance with the
functional requirements contained herein. A general description of the test conditions and test requirements
is given in Annex A (normative).
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
references are cited at the appropriate places in the text and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this ETS
only when incorporated in it by amendments or revision. For undated references the latest edition of the
publication referred to applies.
[1] ETS 300 001: "Attachments to the Public Switched Telephone Network (PSTN);
General technical requirements for equipment connected to an analogue
subscriber interface in the PSTN, (Candidate NET 4)".
[2] ETS 300 114 (1990): "Attachments to the Public Switched Telephone Network
(PSTN); Basic attachment requirements for modems standardized for use on the
PSTN".
[3] CCITT Recommendation V.32 (1988): "A family of 2-wire duplex modems
operating at data signalling rates of up to 9600 bit/s for use on the general
switched telephone network and on leased lines telephone-type circuits".
[4] CCITT Recommendation V.25 (1988): "Automatic answering equipment and/or
parallel automatic calling equipment on the general switched telephone network
including procedures for disabling of echo control devices for both manually and
automatically established calls".
[5] CCITT Recommendation S.33 (1984): "Standardisation of an international text
for the measurement of the margin of start-stop machines using International
Alphabet No 5".
[6] CCITT Recommendation O.153 (1988): "Basic parameters for the measurement
of error performance at bit rates below the primary rate".
3 Definitions and abbreviations
3.1 Definitions
For the purpose of this ETS the definitions in ETS 300 114 [2] apply, together with the following.
NOTE: In addition to the following definitions some other specific definitions are applicable (see
subclauses 5.8.1 and 5.11.1 of this ETS).
Answer mode: when calls are established with automatic facilities, a standard answer mode shall be used
by the modem at the answering station. This mode consists of conventional characteristics (e.g. use of
high channel carrier frequency or particular scrambler generating polynomial) complementary to those used

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ETS 300 002: February 1992
in the standard call mode by the modem at the calling station, in order to ensure proper connection and
inter-working.
If calls are established on the PSTN by operators, or for leased line operation, bilateral agreement on the
use of call mode and answer mode shall be necessary.
Call mode: when calls are established with automatic facilities, a standard call mode shall be used by the
modem at the calling station. This mode consists of conventional characteristics (e.g. use of low channel
carrier frequency or particular scrambler generating polynomial) complementary to those used in the
standard answer mode by the modem at the answering station, in order to ensure proper connection and
inter-working.
If calls are established on the PSTN by operators, or for leased line operation, bilateral agreement on the
use of call mode and answer mode shall be necessary.
Data Terminal Equipment (DTE): in the context of this ETS, the expression "DTE" is used to define the
origin and destination of signals present at the digital interface of a modem. This expression does not
require that a "commercial data terminal" be present to receive or generate such signals; a tester or any
other suitable device may monitor or generate such signals.
Modem: a functional unit that modulates and demodulates signals in order to enable digital data to be
transmitted over analogue transmission facilities.
Modem Conformance Tester (MCT): this is essentially a simulator designed to meet the requirements of
a modem to the same recommendation as the modem under test. All individual sub-systems within it are
both accessible (e.g. provide test points and permit functions to be enabled or disabled when required)
and externally controllable (e.g. permit sequences such as the start up procedure to be selectively
repeated). These within a conformance tester may be constructed as discrete items of equipment, so as
to permit their assembly into varying configurations required to suit the tests (e.g. the asynchronous to
synchronous converter may be simply applied to a synchronous CCITT Recommendation V.32 [3]
conformance tester to achieve an asynchronous CCITT Recommendation V.32 [3] conformance tester).
As an interim measure, until the conformance tester is defined, its definition agreed to be appropriate by
ETSI, and such a tester is available, a modem used for reference may be used in its place. In the absence
of previous approval to Category II of the modem used for reference, in the relevant modes of
use/operation, the testing authority shall ensure that the modem used for reference complies with the
relevant ETS to the extent necessary for the performance of the test.
Modem used for reference: a modem used for some of the tests specified herein or in another modem
specific ETS. A modem used for reference may, at the discretion of the applicant, be provided by the
testing authority or by himself. It shall be designed:
- to meet the requirements of the same CCITT Recommendation(s) as the modem under test, to the
extent necessary for performing the tests;
- to provide the functionalities for a modem used for reference that are specified in the relevant
testing Clauses; and
- to provide an interface which is accessible and of a type suitable for use in the tests (e.g. CCITT
Recommendation V.24).
Where the applicant has provided the modem used for reference and the test fails, the testing authority
may not be in a position to determine the precise reason for failure.
Modes of operation: modes specified in this modem specific ETS, that have an influence upon line signals
present at the PSTN interface.
Modes of use: modes specified in this modem specific ETS, that have an influence upon conditions
present at a digital interface. For example, a "conventional" CCITT Recommendation V.24 interface or a
PC bus interface in the case of an integral modem .

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ETS 300 002: February 1992
On-line state: the on-line state or condition is defined as an electrical condition into which, when
connected to the network, a modem is placed such that it draws enough current to be capable of activating
the exchange.
NOTE: Usually, a modem in on-line state is potentially capable of sending or receiving
speechband information to, or from, the network.
Silence: signals which in the relevant frequency band have an in-band power level which is at least 30 dB
below the level of the transmitted signal at the point of measurement. This term is used to describe periods
where signals are not transmitted during the handshaking sequences.
3.2 Abbreviations
For the purpose of this ETS the following abbreviations apply.
AMM Answer Mode Modem
CCITT Comité Consultatif International Télégraphique et Téléphonique
CCT Circuit
CEPT Conférence Européenne des Administrations des Postes et des
Télécommunications
CMM Call Mode Modem
DCE Data Circuit-Terminating Equipment
DTE Data Terminal Equipment
ETS European Telecommunication Standard
ETSI European Telecommunications Standards Institute
GPA General Polynomial Answer mode modem
GPC General Polynomial Call mode modem
MCT Modem Conformance Tester
MUT Modem Under Test
NET Norme Européene de Télécommunication
PSTN Public Switched Telephone Network
4 General requirements
4.1 References to other ETSs
The modem shall comply with ETS 300 114 [2], Clause 4.
NOTE: ETS 300 114 in turn refers to ETS 300 001 [1] for the majority, if not all, of its
requirements.
4.2 Information to be provided by the applicant
4.2.1 Information required for testing purposes
The applicant shall declare for which of the modes of operation/use identified in this ETS approval to
Category II is sought.
Compliance is considered to have been accomplished by provision of the relevant information.
NOTE: This could be accomplished by completion of forms such as those provided in Annex B
(informative).
4.2.2 Instructions for use
Instructions for use shall be made available with the apparatus. The instructions for use shall include:
a) the apparatus or types of apparatus to which the instructions apply;
b) any information specifically indicated in this ETS for inclusion in the "Instructions for use"; and

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c) any national restrictions on the use of the apparatus.
Any additional information that has been included shall be disregarded unless it is the subject of another
ETS.
Compliance shall be checked by inspection.
5 Functional requirements specific to Category II modems
5.1 General requirements
To comply with the requirements of this ETS, it shall be necessary that the modem provide:
- duplex mode of operation by means of the modulation scheme specified in CCITT Recommendation
V.32 [3];
- channel separation by echo cancellation techniques;
- quadrature amplitude modulation;
- signalling rates of 4800 bit/s and/or 9600 bit/s;
- use of the rate sequence during call establishment to decide the data rate and method of coding;
- means by which the channels may be selected either manually and/or automatically, where a
modem is capable of transmitting in either of the two channels;
- means to respond to a request for a retrain;
- means to respond to a request for an instigation of a digital loop 2.
NOTE 1: The general requirements described above are a subset of CCITT Recommendation
V.32 [3]. In the requirements which follow any deviations from the strict interpretation of
CCITT Recommendation V.32 [3] have been identified.
NOTE 2: In the following, references are made to interchange circuits between the modem and
the DTE, as defined in CCITT Recommendation V.24. However, not all modems
provide an interface with such circuits. For these cases the references to CCITT
Recommendation V.24 type interchange circuits indicate equivalent operation of a DTE
and of a modem where this exists.
5.2 Modes of operation/use
The following modes of operation are identified:
- 9600 bit/s Trellis coded, call;
- 9600 bit/s Trellis coded, answer;
- 9600 bit/s non-redundant coding, call;
- 9600 bit/s non-redundant coding, answer;
- 4800 bit/s non-redundant coding, call;
- 4800 bit/s non-redundant coding, answer.

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It shall be possible to configure the modem to operate at either 4800 bit/s or 9600 bit/s. Optionally the
modem may operate at both 4800 bit/s and 9600 bit/s. Where the modem operates at 9600 bit/s using
trellis coding then non-redundant coding at 9600 bit/s shall also be provided.
For each mode of operation identified for approval to Category II, the modem shall provide at least one of
the following modes of use:
a) asynchronous with 8 bits per character;
b) asynchronous with 9 bits per character;
c) asynchronous with 10 bits per character;
d) asynchronous with 11 bits per character;
e) synchronous.
In the asynchronous (start-stop) modes of use, the modem shall accept a data stream from the DTE at a
nominal rate of 9600 bits per second and/or 4800 bits per second. The asynchronous data to be
transmitted shall be converted into a synchronous data stream in accordance with subclause 5.9 suitable
for transmission.
Demodulated data shall be decoded in accordance with subclause 5.5, then descrambled in accordance
with subclause 5.6, it shall then be passed for reconversion into an asynchronous data stream in
accordance with subclause 5.9.
In the synchronous modes of use, the modem shall accept synchronous data from the DTE. The data shall
then be scrambled in accordance with subclause 5.6 and passed to the modulator for encoding in
accordance with subclause 5.5.
Demodulated data shall be decoded in accordance with subclause 5.5, then descrambled in accordance
with subclause 5.6.
The modem shall respond to a request to execute a retrain. Optionally, the modem may also provide
facilities to instigate a retrain during data transmission if the modem detects a loss of equalization.
NOTE: This facility can also be used to effect a change of rate from 9600 bit/s to 4800 bit/s or
vice versa, without disconnection from the PSTN.
It shall be the applicant's responsibility to specify for which of the above mentioned modes of operation/use
approval for Category II is sought.
5.3 Line signals
5.3.1 Transmitted carrier frequency
The carrier frequency transmitted shall be 1800 Hz ± 1 Hz.
Compliance shall be checked by the method described in Annex A, Clause A.2.
5.3.2 Receiver carrier tolerance
The receiver shall be able to operate correctly with a received carrier frequency in the range of 1800 Hz ±
7 Hz.
Compliance shall be checked by the method described in Annex A, Clause A.3.
5.3.3 Transmitted spectrum
The national network specific spectral power limits are specified in ETS 300 114 [2], Clause 4.

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ETS 300 002: February 1992
NOTE: ETS 300 114 [2], Clause 4 in turn refers to ETS 300 001 [1].
There are no requirements in this ETS relating to the spectrum of signals presented to the PSTN over and
above those for PSTN access invoked by Clause 4 of ETS 300 001 [1].
5.4 Line signalling rates
The signalling rates transmitted to line shall be 2400 baud ± 0,01 %.
Compliance shall be checked by the method described in Annex A, Clause A.4.
5.5 Encoding of data
The signal element coding shall be as defined in CCITT Recommendation V.32 [3], paragraph 2.4.1.1
(non-redundant coding for 9600 bit/s operation) and/or paragraph 2.4.2 (4800 bit/s operation).
Trellis coding as defined in CCITT Recommendation V.32 [3], paragraph 2.4.1.2 may optionally be
provided.
The provision of non-redundant coding at 9600 bit/s shall be mandatory if trellis coding at 9600 bit/s has
been provided.
Compliance shall be checked by the method described in Annex A, Clause A.5.
5.6 Scrambler and descrambler
A self-synchronizing scrambler and a self-synchronizing descrambler as specified in CCITT
Recommendation V.32 [3], paragraph 4, Introduction, shall be provided in the transmitting part and the
receiving part, respectively, of the modem.
Compliance shall be checked by performing the test for encoding of data, described in Annex A, Clause
A.6.
5.7 Channel allocation
5.7.1 Channel selection
A modem which is capable of being configured as both a Call Mode Modem (CMM) and an Answer Mode
Modem (AMM) shall provide facilities for at least one of the following techniques of channel selection:
a) manual selection of the channels using facilities provided on the modem;
b) selection of the channels by the DTE (equivalent: CCT 126 control);
c) automatic selection of the channels as described in subclause 5.7.2.
NOTE: Other means of channel selection may also be provided but verification of the correct
functioning of such facilities is not a requirement of this ETS.
For techniques a) and b), compliance shall be checked by the method described in Annex A, Clause A.7.
5.7.2 Automatic channel selection
A modem providing this facility shall, in the absence of manual intervention or a contrary command e.g. via
a digital interface (e.g. an equivalent to control using CCT 126), be automatically configured as:
a) a CMM when exchanging data on-line to another compatible modem, and when the modem has
entered the on-line state other than in response to an incoming PSTN call;

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ETS 300 002: February 1992
b) an AMM when exchanging data on-line to another compatible modem, and when the modem has
entered the on-line state in response to an incoming PSTN call.
Compliance shall be checked by the method described in Annex A, Clause A.7.
5.8 Hand-shaking sequences
5.8.1 Definitions
In the following sequences the signals described shall be sent contiguously unless the description indicates
that a period of silence be present.
NOTE: The following definitions refer to the signal states A,B,C and D, which are defined in
CCITT Recommendation V.32 [3], figures 1 and 3.
T: T is the reciprocal of the transmitter baudrate. This is also known as the symbol interval.
AA: this signal is generated by transmitting signal state A with the differential encoder inhibited.
CC: this signal is generated by transmitting signal state C with the differential encoder inhibited.
AC: this signal is generated by alternately transmitting signal state A and signal state C with the differential
encoder inhibited.
CA: this signal is generated by alternately transmitting signal state C and signal state A with the differential
encoder inhibited for an even number of symbol intervals (i.e. 2 T, 4 T, etc.).
S: this signal is generated by alternately transmitting signal state A and signal state B with the differential
encoder inhibited.
S(bar): this signal is generated by alternately transmitting signal state C and signal state D with the
differential encoder inhibited for 16 T.
TRN: the scrambler is first set with all registers to "0". The TRN signal is derived by applying binary 1 to
the relevant scrambler with the differential encoder inhibited. The data stream is split into dibits. For the
first 256 T only the first bit of each dibit is considered and where this bit is a "1" signal state "C" is
transmitted and where it is a "0" signal state "A" is transmitted. After 256 T both bits are taken into
account. If both the bits are "0"s", signal state A is transmitted; if both the bits are "1"s", signal state C is
transmitted; if the first bit is a "0" and the second bit a "1", signal state B is transmitted; finally if the first bit
is a "1" and the second bit a "0", signal state D is transmitted. The final symbol of this sequence shall be
used to initialise the differential encoder.
E: this signal is a single 16 bit sequence. It is sent at 4800 bit/s differentially encoded and scrambled using
the relevant scrambling sequence. The signal is encoded in the same format as a rate sequence but it
indicates a single rate at which the subsequent scrambled binary 1 shall be transmitted.
B1: the equivalent signal to Binary 1 being applied to the transmit data lead. The signal is transmitted at
the data rate indicated by signal E after being scrambled and differentially encoded and, where relevant,
passed through a convolutional encoder.
Rate Sequences: this is a series of 16 bits which are transmitted by one modem to provide the distant
modem with information about its capabilities . For the purpose of this ETS, in table 1 below the bits
marked "1" or "0" are fixed, whilst the bits marked "*" are able to assume a value of either "0" or "1". A
modem shall not assume that it has detected a valid rate signal until at least two consecutive Rate
Sequences are found to be identical. In the event that no compatible rate exists, the setting of all of the
bits marked "*" to a "0" shall signal the intention of clearing down the call.

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ETS 300 002: February 1992
Table 1: Coding of rate sequences.
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡                                               ‡
‡                     Bits                        ‡
‡                                               ‡
‡B0  B1  B2  B3  B4  B5  B6  B7  B8  B9   B10  B11  B12  B13  B14  B15‡
‡                                               ‡
‡ 0   0   0   0   *   *   *   1   *   *   *   1   *   0   0   1 ‡
‡                                               ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
For each bit a "1" indicates the availability of that rate or option and a "0" that the rate or option is not
available.
When bit 8 is a "0", bit 4 indicates the availability of 2400 bit/s.
Bit 5 indicates the availability of 4800 bit/s.
Bit 6 indicates the availability of 9600 bit/s.
Bit 8 indicates the availability of trellis coding.
Bits 9, 10, 12, have been assigned functions in CCITT Recommendation V.32bis ("A duplex modem
operating at data signalling rates of up to 14 400 bit/s for use on the general switched telephone network
and on leased point-to-point 2 wire telephone type circuits.", Geneva, 1991) and shall not be assigned a
use contrary to those listed below.
Use of Bits 9, 10 and 12 within CCITT Recommendation V.32bis:
- Bit 9 indicates the availability of 7200 bit/s;
- Bit 10 indicates the availability of 12000 bit/s;
- Bit 12 indicates the availability of 14400 bit/s.
Although bits 13 and 14 have not yet been assigned a use by CCITT, modems seeking Category II
approval shall have set these bits to "0".
NOTE: Since the use of bits 9, 10, 12, 13, 14 is not specified in CCITT Recommendation V.32
[3], the requirement relating to these bits are additional to those of the CCITT
Recommendation V.32 [3].
R1: this sequence is transmitted by the Answer Mode Modem (AMM) at 4800 bit/s scrambled using
General Polynomial Answer mode modem (GPA) and differentially encoded. The relevant bits marked "*"
shall be set to a "1" whenever the modem is currently capable of working at the rate or mode indicated.
R2: this sequence is transmitted by the Call Mode Modem (CMM) at 4800 bit/s scrambled using General
Polynomial Call mode modem (GPC) and differentially encoded. This signal shall indicate which rates of
those indicated by rate signal R1 the call mode modem is able to support.
R3: this sequence is transmitted by the Answer Mode Modem at 4800 bit/s scrambled using GPA and
differentially encoded. This signal shall indicate which of the rates indicated in rate signal R2 the modem
has chosen to work at.
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ETS 300 002: February 1992
5.8.2 Auto-calling and auto-answering procedures
5.8.2.1 Auto-calling - calling tone
This ETS does not require the provision of the calling tone defined in CCITT Recommendation V.25 [4].
5.8.2.2 Auto-calling - recognition of answering tone
For modems to be used for automatically originated calls, the modem, or its associated call establishment
equipment, shall comply with the requirements for answering tone detection given in ETS 300 114 [2],
subclause 5.2.1.
In addition, the Modem Under Test (MUT) shall start the start-up procedure (sending AA signal) during the
answer-tone or within 1 s after receiving the end of the answer-tone.
NOTE: This requirement is in addition to CCITT Recommendation V.32 [3].
5.8.2.3 Auto-answering
For modems to be used for automatically answered calls, the modem, or its associated call answering
equipment, shall comply with the requirements for answering tone generation given in ETS 300 114 [2],
subclause 5.2.2, except for the duration of the 2100 Hz tone, which may be shorter than 2,6 s if the calling
station response is detected for at least 100 ms.
5.8.3 Start-up procedure
After the completion of any dialogue between the modem and the DTE for the purpose of establishing the
connection, the modem shall be indicating that:
a) it is not detecting a valid line signal (equivalent: CCT 109 OFF);
b) it is not ready to transmit data (equivalent: CCT 106 OFF).
NOTE: For a modem to indicate that it is ready to transmit data (equivalent: turning ON
CCT 106) it may be necessary for the DTE to indicate that it wishes to transmit data
(equivalent: turning ON CCT 105).
5.8.3.1 Call Mode Modem (CMM)
5.8.3.1.1 AA signal
After connection to line the modem shall condition itself to detect answer tone. After detection of answer
tone for a period of at least 1 s, the MUT shall transmit the AA signal.
Compliance shall be checked by the method described in Annex A, subclause A.8.2.1.1.
5.8.3.1.2 Round trip delay determination
The modem shall initiate the start-up sequence by transmitting signal AA. When presented with signal AC
the modem shall cause a timer to be initiated. The modem shall monitor the line for a phase reversal in the
incoming signal. Presentation of signal CA to the line terminals of the modem shall cause the modem to
cease transmitting signal AA and commence transmitting signal CC. The delay between presentation of
signal CA to the line terminals of the modem and signal CC appearing at the line terminals shall be 64 T ±
2 T. The modem shall again monitor the line for a phase reversal in the incoming signal. Presentation of
signal AC to the line terminals of the modem shall cause the modem to note the time indicated by the timer
and cease transmitting signals. The time period recorded by this timer is the effective round trip delay for
this modem hereinafter referred to as NT and includes 64 T ± 2 T turn round delay in the remote modem.
Compliance shall be checked by the method described in Annex A, subclause A.8.2.1.2.

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ETS 300 002: February 1992
5.8.3.1.3 Rate negotiation
The modem shall monitor the incoming signals for signal S followed by a phase reversal. The receiver of
the modem shall now be conditioned to receive the TRN sequence, followed by rate signal R1.
When the modem has detected at least two consecutive identical rate sequences R1, the modem shall
transmit either:
a) signal S for a period of NT + 256 T; or,
b) signal S for a period of NT followed by a signal (special echo canceller training sequence) which
maintains the energy transmitted to line in such a way that the sum of the powers in the bands 500
Hz to 700 Hz, 1700 Hz to 1900 Hz and 2900 Hz to 3100 Hz is at least 1 dB less than the sum of the
power in the bands 700 Hz to 1700 Hz and 1900 Hz to 2900 Hz. The duration of this optional
sequence shall not exceed 8192 T. This shall be followed by a further period of signal S for 256 T.
After transmission of one of the two sequences above, the modem shall transmit Signal S(bar), followed
by the TRN sequence for a period of not less than 1280 T and not more than 8192 T.
After completing the transmission of the TRN sequence the modem shall indicate to the DTE that it
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