SIST ETS 300 117 E2:2003

SLOVENSKI STANDARD
01-december-2003
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Public Switched Telephone Network (PSTN); Category II specification for 2 400 bits per
second duplex modems standardized for use on the PSTN
Ta slovenski standard je istoveten z: ETS 300 117 Edition 2
ICS:
33.040.35 Telefonska omrežja Telephone networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 117
TELECOMMUNICATION May 1996
STANDARD Second Edition
Source:ETSI TC-TE Reference:RE/TE-05048
ICS: 33.020
modem, PSTN, testing
Key words:
Public Switched Telephone Network (PSTN);
Category II specification for 2 400 bits per second
duplex modems standardized for use on the PSTN
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 1996. All rights reserved.

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ETS 300 117: May 1996
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 Committee Support Dept." at the address shown on the title page.

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ETS 300 117: May 1996
Contents
Foreword .7
1 Scope .9
2 Normative references.9
3 Definitions and abbreviations .10
3.1 Definitions .10
3.2 Abbreviations .10
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 .11
5.1 General requirements .11
5.2 Modes .12
5.3 Line signals.12
5.3.1 Carrier frequencies.12
5.3.2 Guard tone .13
5.3.2.1 Guard tone - call mode modem.13
5.3.2.2 Guard tone - Answer Mode Modem (AMM).13
5.3.3 Transmitted spectrum .13
5.4 Line signalling rates .13
5.5 Encoding and decoding of data .13
5.6 Threshold of the received line signal detector .13
5.7 Channel allocation .14
5.7.1 Channel selection.14
5.7.2 Automatic channel selection.14
5.8 Hand-shaking sequences .14
5.8.1 Auto-calling and auto-answering procedures.14
5.8.1.1 Auto-calling - calling tone.14
5.8.1.2 Auto-calling - recognition of answering tone.14
5.8.1.3 Auto-answering.14
5.8.2 Start-up procedures.15
5.8.2.1 Call Mode Modem (CMM) .15
5.8.2.1.1 AMM set to 2 400 bit/s (CCITT
Recommendation V.22bis) .15
5.8.2.1.2 AMM set to 1 200 bit/s (CCITT
Recommendation V.22 or V.22bis).15
5.8.2.2 Answer Mode Modem (AMM).16
5.8.2.2.1 CMM set to 2 400 bit/s (CCITT
Recommendation V.22bis) .16
5.8.2.2.2 CMM set to 1 200 bit/s.16
5.8.3 Retrain sequence (2 400 bit/s operation) .17
5.8.3.1 Initiating signal .17
5.8.3.2 Response signal .17
5.8.4 Rate change request.17
5.8.4.1 2 400 bit/s to 1 200 bit/s.18
5.8.4.1.1 Instigation of a rate change .18
5.8.4.1.2 Response to a request for rate change 18
5.8.4.2 1 200 bit/s to 2 400 bit/s.18
5.8.4.2.1 Instigation of a rate change .18
5.8.4.2.2 Response to a request for rate change 19
5.9 Transmission of start-stop characters .19

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ETS 300 117: May 1996
5.10 Scrambler and de-scrambler. 19
5.11 Test loop 2. 20
5.11.1 Instigation of a remote loop 2 . 20
5.11.2 Termination of a remote loop 2. 20
5.12 Receiver performance. 21
Annex A (normative): Testing methods . 22
A.1 General testing conditions . 22
A.1.1 General notes. 22
A.1.2 Proposed order for performing the tests . 22
A.1.3 Limitation of number of tests. 24
A.1.3.1 Introduction . 24
A.1.3.2 General rules . 24
A.1.3.3 Specific rules . 24
A.2 Test for subclause 5.3.1 (Carrier frequencies) . 25
A.2.1 Test for subclause 5.3.1 using the MCT . 25
A.2.2 Test for modems where the scrambler can be inhibited . 25
A.2.3 Tests for modems where test points are accessible. 25
A.2.4 Test for modems where neither subclauses A.2.2 nor A.2.3 applies. 26
A.3 Test for subclause 5.3.2 (Guard tone). 26
A.3.1 Test for subclause 5.3.2.1 (Guard tone, CMM). 26
A.3.2 Test for subclause 5.3.2.2 (Guard tone, AMM). 26
A.4 Test for subclause 5.4 (Line signalling rates). 26
A.5 Test for subclause 5.5 (Encoding and decoding of data) . 27
A.6 Test for subclause 5.6 (Threshold of received line signal detector) . 27
A.7 Test for subclause 5.7 (Channel allocation) . 27
A.7.1 Test for subclause 5.7.1 (General). 27
A.7.2 Test for subclause 5.7.2 (Automatic channel selection) . 28
A.8 Test for subclause 5.8 (Hand-shaking sequences). 28
A.8.1 Tests for subclause 5.8.2 (Start-up procedures). 28
A.8.1.1 Test for subclause 5.8.2.1 (Call Mode Modem under test). 28
A.8.1.1.1 Test for subclause 5.8.2.1.1 (CMM calling a CCITT
Recommendation V.22bis AMM at 2 400 bit/s). 29
A.8.1.1.2 Test for subclause 5.8.2.1.2 (CMM calling a CCITT
Recommendation V.22 or V.22bis AMM at 1 200 bit/s). 29
A.8.1.2 Test for subclause 5.8.2.2 (Answer Mode Modem under test). 30
A.8.1.2.1 Test for subclause 5.8.2.2.1 (AMM called by a CCITT
Recommendation V.22bis CMM at 2 400 bit/s) . 30
A.8.1.2.2 Test for subclause 5.8.2.2.2 (AMM called by a CCITT
Recommendation V.22 or V.22bis CMM at 1 200 bit/s). 30
A.8.2 Tests for subclause 5.8.3 (Retrain sequence) . 31
A.8.2.1 Tests for subclause 5.8.3.1 (Initiating signal) . 31
A.8.2.2 Tests for subclause 5.8.3.2 (Response signal) . 31
A.8.3 Tests for subclause 5.8.4 (Rate change request) . 32
A.8.3.1 Tests for subclause 5.8.4.1 (2 400 bit/s to 1 200 bit/s). 32
A.8.3.1.1 Tests for subclause 5.8.4.1.1 (Instigation of a rate change
from 2 400 bit/s to 1 200 bit/s) . 32
A.8.3.1.2 Tests for subclause 5.8.4.1.2 (Response to a request for
a rate change from 2 400 bit/s to 1 200 bit/s) . 33
A.8.3.2 Tests for subclause 5.8.4.2 (1 200 bit/s to 2 400 bit/s). 34
A.8.3.2.1 Tests for subclause 5.8.4.2.1 (Instigation of a rate change
from 1 200 bit/s to 2 400 bit/s) . 34
A.8.3.2.2 Tests for subclause 5.8.4.2.2 (Response to a request for
a rate change from 1 200 bit/s to 2 400 bit/s) . 35

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ETS 300 117: May 1996
A.9 Test for subclause 5.10 (Scrambler and de-scrambler).36
A.9.1 Test for modems which can be operated in the synchronous mode of use .36
A.9.2 Test for modems which can only be operated in a asynchronous mode of use.36
A.10 Test for subclause 3.11 (Test loop 2).37
A.10.1 Instigation of remote test loop 2.37
A.10.1.1 Transmission of the test loop initiation signal (Controlling modem under
test) .37
A.10.1.2 Response to the test loop initiation signal (Controlled modem under test) .37
A.10.2 De-activation of remote test loop 2 .38
A.10.2.1 Transmission of the de-activation signal (Controlling modem under test) .38
A.10.2.2 Response to the de-activation signal (Controlled modem under test) .38
Annex B (informative): Derivation of timings.39
Annex C (informative): Example proforma for the declaration of modes of operation/use .40
Annex D (informative): Bibliography.42
History.43

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ETS 300 117: May 1996
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ETS 300 117: May 1996
Foreword
This second edition European Telecommunication Standard (ETS) has been produced by the Terminal
Equipment (TE) Technical Committee of the European Telecommunications Standards Institute (ETSI).
The objective of this specification, the application of which is entirely voluntary, is to provide the users with
an added degree of assurance that modems in compliance with this specification can interwork with each
other, under most network conditions.
This ETS contains the technical characteristics required for end-to-end interworking over the Public
Switched Telephone Network (PSTN), for 2 400 bits per second duplex modems standardized for use
over the PSTN.
These requirements are based upon, and do not conflict with, CCITT Recommendation V.22bis [2].
Additionally, requirements are included relating to end-to-end inter-operability over PSTN connections.
Such requirements are in excess of the CCITT/ITU-T Recommendations.
Except where otherwise stated, a modem which complies with CCITT Recommendation V.22bis [2]
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 which are common to both Category I and Category II
modems, which are contained in clause 4 of final draft prETS 300 114 [1]. The definition of Category I and
Category II modems can be found in the foreword of final draft ETS 300 114 [1].
Clause 5 of this ETS contains Category II requirements specific to 2 400 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 final draft prETS 300 114 [1] which contains the relevant
requirements.
Transposition dates
Date of adoption of this ETS: 26 April 1996
Date of latest announcement of this ETS (doa): 31 August 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 29 February 1997
Date of withdrawal of any conflicting National Standard (dow): 29 February 1997

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ETS 300 117: May 1996
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ETS 300 117: May 1996
1 Scope
This ETS contains the technical characteristics required for end-to-end interworking over the Public
Switched Telephone Network (PSTN) of 2 400 bits per second (bit/s) duplex modems standardized for
use over the PSTN, in accordance with CCITT Recommendation V.22bis [2].
The term "modem" in the context of this ETS includes all physical implementation practices for a voice
band modem, which is conductively connected to the PSTN.
This ETS specifies four modes of operation each with up to 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.
2 Normative references
This ETS incorporates by dated or undated reference, provisions from other publications. These
normative 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 amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] Final draft prETS 300 114 (1996): "Public Switched Telephone Network (PSTN);
Basic Category I and Category II specification for modems standardized for use
on the PSTN".
[2] CCITT Recommendation V.22bis (1988): "2 400 bits per second duplex modem
using the frequency division technique standardized for use on the General
Switched Telephone Network and on point-to-point 2-wire leased telephone-type
circuits".
[3] CCITT Recommendation V.22 (1984): "1 200 bits per second duplex modem
standardized for use in the General Switched Telephone Network and on
point-to-point 2-wire leased telephone-type circuits".
[4] 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".
[5] CCITT Recommendation V.25 (1984): "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".
[6] CCITT Recommendation S.33 (1984): "Standardization of an international text
for the measurement of the margin of start-stop machines using International
Alphabet No 5".
[7] CCITT Recommendation V.52 (1984): "Characteristics of distortion and
error-rate measuring apparatus for data transmission".

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ETS 300 117: May 1996
3 Definitions and abbreviations
3.1 Definitions
For the purpose of this ETS the definitions of final draft prETS 300 114 [1] apply, together with the
following:
Initiation and Acknowledgement Signal (S1): Comprises an unscrambled repetitive double dibit pattern
of '00' and '11' at 1 200 bit/s.
Modem Conformance Tester (MCT): This is essentially a modem to the same recommendation as the
modem under test, but the 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). The sub-systems 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.22 [3] conformance tester to achieve an
asynchronous CCITT Recommendation V.22 [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 case
that the modem used for reference has not been shown to conform to the ETS in the relevant modes of
operation/use, in the relevant modes of use/operation, the testing authority ensures that the modem used
for reference complies with the relevant ETS to the extent necessary for the performance of the test.
3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AMM Answer Mode Modem
CcT Circuit
CMM Call Mode Modem
DCE Data Circuit-Terminating Equipment
DTE Data Terminal Equipment
MCT Modem Conformance Tester
PSTN Public Switched Telephone Network
TE Terminal Equipment
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ETS 300 117: May 1996
4 General requirements
4.1 References to other ETSs
The modem shall comply with final draft prETS 300 114 [1], clause 4.
NOTE: Final draft prETS 300 114 [1] in turn refers to ETS 300 001 [4] 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 the modem is
supposed to undergo tests.
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 C
(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";
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, the modem shall provide:
a) duplex mode of operation with continuous carrier, by means of the modulation scheme specified in
CCITT Recommendation V.22bis [2];
b) channel separation by frequency division;
c) 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;
d) provision of a guard tone of 1 800 Hz ± 20 Hz, which a modem is to transmit while transmitting in
the high channel;
e) signalling rates of 2 400 bit/s and 1 200 bit/s;
f) the interchange circuits (or equivalent) that are required to change state after an identifiable event
or point in time, shall have changed state within a maximum of 3 seconds of that event, unless
otherwise specified (see note 4).
NOTE 1: The general requirements described above are a subset of those given in CCITT
Recommendation V.22bis [2]. In the requirements which follow any deviations from the
strict interpretation of the CCITT Recommendation V.22bis [2] have been identified.

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ETS 300 117: May 1996
NOTE 2: In the following, references are made to interchange circuits between the modem and
the Data Terminal Equipment (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.
NOTE 3: To perform certain tests specified herein, it is desirable that it be possible to disable
the transmit scrambler of the modem.
NOTE 4: This requirement is in addition to CCITT Recommendation V.22 [3].
5.2 Modes
It shall be possible to configure the modem to operate at 2 400 bit/s and at 1 200 bit/s in at least one of
the following modes of use for either the call mode or the answer mode or, optionally, both the call and
answer modes:
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 2 400 bit/s and 1 200 bit/s. The asynchronous data to be transmitted shall be converted
into a synchronous data stream in accordance with subclause 5.9 to be suitable for transmission.
Demodulated data shall be decoded in accordance with subclause 5.5, then descrambled in accordance
with subclause 5.10, 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 5.10 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 5.10.
Optionally, the modem may also provide facilities to instigate:
a) a retrain procedure during data transmission if the modem detects a loss of equalization; and/or
b) a rate change in a remote modem and also to respond to a rate change request. This facility, when
provided, permits modems to alter their rate of operation from 2 400 bit/s to 1 200 bit/s, and vice
versa, without disconnection from the PSTN.
It shall be the applicant's responsibility to specify for which of these modes of operation/use testing for
conformance to this ETS is required.
5.3 Line signals
5.3.1 Carrier frequencies
The carrier frequencies shall be 1 200 Hz ± 0,5 Hz for the low channel and 2 400 Hz ± 1 Hz for the high
channel.
Compliance shall be checked by the method described in annex A, clause A.2.

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ETS 300 117: May 1996
5.3.2 Guard tone
5.3.2.1 Guard tone - call mode modem
When the modem is transmitting in the low channel, it shall not transmit the guard tone specified in
subclause 5.3.2.2.
Compliance shall be checked by the method described in annex A, subclause A.3.1.
5.3.2.2 Guard tone - Answer Mode Modem (AMM)
When the modem is transmitting in the high channel, a guard tone at 1 800 Hz ± 20 Hz shall be
transmitted simultaneously. The level of the guard tone shall be 6 dB ± 1 dB below the level of the data
signal in the high channel.
Optionally, facilities may be provided to disable the transmission of the guard tone of 1 800 Hz. Since the
provision of the guard tone is mandatory, all tests in this ETS shall be carried out with guard tone present.
Compliance shall be checked by the method described in annex A, subclause A.3.2.
The overall level of the guard tone and the data signal of a CCITT Recommendation V.22bis [2] modem
shall remain in compliance with the in-band spectral power limits for the network to which they are being
connected (see final draft prETS 300 114 [1], clause 4).
NOTE: The purpose of the guard tone is to inhibit the false operation of in-band signalling
systems such as in international networks (see CCITT Recommendation Q.144). It is
thought by some that a marginal performance advantage may be gained as a result of
the slightly higher transmit level possible when the guard tone is disabled and therefore
this option is permitted.
5.3.3 Transmitted spectrum
The national network specific spectral power limits are specified in final draft prETS 300 114 [1], clause 4.
NOTE: Final draft prETS 300 114 [1], clause 4 in turn refers to ETS 300 001 [4]. 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 subclause 4.1.
5.4 Line signalling rates
The signalling rates transmitted to line shall be 2 400 bit/s and 1 200 bit/s ± 0,01 %.
Compliance shall be checked by the method described in annex A, clause A.4.
5.5 Encoding and decoding of data
The encoding and decoding of data shall be in accordance with CCITT Recommendation V.22bis [2],
section 2.5.2 and table 1/V.22bis.
Until a Modem Conformance Tester (MCT) is available, compliance shall be checked by inspection of the
applicant's declaration of conformance. When a MCT is available, compliance shall be checked by the
method described in annex A, clause A.5.
5.6 Threshold of the received line signal detector
The modem shall comply with the requirements of final draft prETS 300 114 [1], subclause 5.4, when
receiving a data signal corresponding to scrambled binary 1 at 2 400 bit/s and at 1 200 bit/s in the
respective receive channel for the modem.
Compliance shall be checked by the method described in annex A, clause A.6.

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ETS 300 117: May 1996
5.7 Channel allocation
A Call Mode Modem (CMM) shall be capable of transmitting signals in the low channel and responding to
signals received in the high channel. An AMM shall be capable of transmitting signals in the high channel
and responding to signals received in the low channel.
5.7.1 Channel selection
A modem which is capable of being configured as both a CMM and an 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, subclause
A.7.1.
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;
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, subclause A.7.2.
5.8 Hand-shaking sequences
In the following sequences the signal described shall be sent contiguously unless the description indicates
that a period of silence be present.
5.8.1 Auto-calling and auto-answering procedures
5.8.1.1 Auto-calling - calling tone
This ETS does not require the provision of the calling tone defined in CCITT Recommendation V.25 [5].
5.8.1.2 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 final draft
prETS 300 114 [1], subclause 5.2.1.
5.8.1.3 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 final draft
prETS 300 114 [1], subclause 5.2.2.

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ETS 300 117: May 1996
5.8.2 Start-up procedures
Initially, the modem shall indicate that:
a) it is not detecting a valid carrier 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) requires that the DTE has indicated that it wishes to transmit data
(equivalent: turning ON CcT 105).
5.8.2.1 Call Mode Modem (CMM)
After connection to line and when presented with contiguous unscrambled binary 1 at 1 200 bit/s and
guard tone from an AMM, the CMM shall remain silent for a minimum of 591 ms. The CMM shall then
transmit Signal S1 (see clause 3) for 100 ms ± 3 ms, followed by scrambled binary 1 at 1 200 bit/s.
The handshake sequence which follows depends upon whether the AMM is set to operate at 2 400 bit/s or
at 1 200 bit/s. This is described in subclauses 5.8.2.1.1 and 5.8.2.1.2.
5.8.2.1.1 AMM set to 2 400 bit/s (CCITT Recommendation V.22bis)
The MCT (the AMM) shall respond by replacing the unscrambled binary 1 at 1 200 bit/s with Signal S1 for
100 ms ± 3 ms followed by scrambled binary 1 at 1 200 bit/s.
When a change from unscrambled binary 1 at 1 200 bit/s to signal S1 occurs in the data received by the
CMM, it shall continue to transmit the scrambled binary 1 at 1 200 bit/s for 600 ms ± 10 ms timed from the
end of receipt of Signal S1, followed by scrambled binary 1s at 2 400 bit/s for 200 ms ± 10 ms.
At the end of this period, the CMM shall:
a) give an indication to the DTE that the modem has detected a valid carrier signal (equivalent: turning
ON CcT 109);
b) give an indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON
CcT 106); and
c) enter the data transmission phase.
For a CMM, condition a) should always occur before condition b) although the criteria for test is simply that
these indications are now ON.
Compliance shall be checked by the method described in annex A, subclause A.8.1.1.1.
5.8.2.1.2 AMM set to 1 200 bit/s (CCITT Recommendation V.22 or V.22bis)
The MCT (the AMM) shall respond by replacing the unscrambled binary 1 with scrambled binary 1 at
1 200 bit/s.
When a change from unscrambled binary 1 to scrambled binary 1 at 1 200 bit/s occurs in the data
received by the CMM, it shall continue to transmit the scrambled binary 1 at 1 200 bit/s for 1 035 ms ±
50 ms.
At the end of this period, the CMM shall:
a) give an indication to the DTE that the modem has detected a valid carrier signal (equivalent: turning
ON CcT 109);
b) give an indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON
CcT 106); and
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ETS 300 117: May 1996
c) enter the data transmission phase.
For a CMM, condition a) should always occur before condition b) although the criteria for test is simply that
these indications are now ON.
Compliance shall be checked by the method described in annex A, subclause A.8.1.1.2.
5.8.2.2 Answer Mode Modem (AMM)
On completion of the CCITT Recommendation V.25 [5] auto-answering sequence or, when manually
answered, on connection to line, the AMM shall transmit unscrambled binary 1 at 1 200 bit/s and guard
tone.
The handshake sequence which follows this depends upon whether the CMM is set to operate at
2 400 bit/s or at 1 200 bit/s, as described in subclauses 5.8.2.2.1 and 5.8.2.2.2.
5.8.2.2.1 CMM set to 2 400 bit/s (CCITT Recommendation V.22bis)
The MCT (the CMM) shall respond by transmitting Signal S1 for 100 ms ± 3 ms followed by scrambled
binary 1 at 1 200 bit/s.
When a change from Signal S1 to scrambled binary 1 at 1 200 bit/s occurs in the data received by the
AMM, it shall transmit Signal S1 for 100 ms ± 3 ms followed by scrambled binary 1 at 1 200 bit/s such that
the total period for Signal S1 and this scrambled binary 1 is 600 ms ± 10 ms. This shall be followed by a
scrambled binary 1 signal at 2 400 bit/s for 200 ms ± 10 ms.
The MCT shall now also be transmitting scrambled binary 1 at 2 400 bit/s. At the end of this period, the
CMM shall:
a) give an indication to the DTE that the modem has detected a valid carrier signal (equivalent: turning
ON CcT 109);
b) give an indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON
CcT 106); and
c) enter the data transmission phase.
For an AMM, conditions a) and b) should occur almost simultaneously. The order is therefore of no
importance.
NOTE: In the event that the rate change option has been established, the AMM may delay
transmission of the Signal S1 by more than 32 dibit duration after receipt of Signal S1
from the CMM.
Compliance shall be checked by the method described in annex A, subclause A.8.1.2.1.
5.8.2.2.2 CMM set to 1 200 bit/s
The MCT (the CMM) shall respond by transmitting scrambled binary 1 at 1 200 bit/s.
When a change from silence to scrambled binary 1 at 1 200 bit/s occurs in the data received by the AMM,
it shall continue to transmit unscrambled binary 1 at 1 200 bit/s for a further 270 ms ± 40 ms, followed by
scrambled binary 1 at 1 200 bit/s for 765 ms ± 10 ms.
At the end of this period, the CMM shall:
a) give an indication to the DTE that the modem has detected a valid carrier signal (equivalent: turning
ON CcT 109);
b) give an indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON
CcT 106); and
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c) enter the data transmission phase.
For an AMM, conditions a) and b) should occur almost simultaneously. The order is therefore of no
importance.
NOTE: In the event that the rate change option has been established, the AMM may delay
transmission of the Signal S1 by more than 32 dibit duration after receipt of Signal S1
from the CMM.
Compliance shall be checked by the method described in annex A, subclause A.8.1.2.2.
5.8.3 Retrain sequence (2 400 bit/s operation)
The requirements of this clause apply to modems for which the applicant has requested testing of this
facility for conformance to this ETS.
5.8.3.1 Initiating signal
The applicant shall indicate a method by which the modem may be caused to initiate a retrain.
Using the method described by the applicant, while the modem is transmitting at 2 400 bit/s, it is caused to
initiate a retrain. The modem shall, give an indication to the DTE that the modem is not ready to transmit
data (equivalent: turning OFF CcT 106), and transmit Signal S1 (see clause 3) for 100 ms ± 3 ms. This
shall be followed by scrambled binary 1 at 1 200 bit/s for a minimum period of 687 ms which shall be
followed, in turn, by scrambled binary 1 at 2 400 bit/s for 200 ms ± 10 ms.
At the end of this period, the modem shall re-enter the data transfer phase at 2 400 bit/s and give an
indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON CcT 106).
Compliance shall be checked by the method described in annex A, subclause A.8.2.1.
5.8.3.2 Response signal
When the modem detects loss of scrambled data at 2 400 bit/s followed by Signal S1, on detection of the
transition from Signal S1 to scrambled binary 1, the modem shall give an indication to the DTE that the
modem is not ready to transmit data (equivalent: turning OFF CcT 106), and transmit Signal S1 for
100 ms ± 3 ms. This shall be followed by scrambled binary 1 at 1 200 bit/s. The total time for which Signal
S1 and the subsequent scrambled binary 1 signal are transmitted shall be 600 ms ± 10 ms. The modem
shall replace the scrambled binary 1 at 1 200 bit/s by scrambled binary 1 at 2 400 bit/s for 200 ms
± 10 ms.
At the end of this period, the modem shall re-enter the data transfer phase at 2 400 bit/s and give an
indication to the DTE that the modem is now ready to transmit data (equivalent: turning ON CcT 106).
NOTE: In the event that the rate change option has been established, the modem may delay
transmission of the Signal S1 by more than 32 dibit durations after receipt of Signal S1
from the MCT.
Compliance shall be checked by the method described in annex A, subclause A.8.2.2.
5.8.4 Rate change request
NOTE: The following subclauses relate to an optional feature published in CCITT
Recommendation V.22bis [2]. This enables a V.22bis modem to signal a rate change
request in the data channel to a remote V.22bis modem.
In order for this facility to conform to the requirements of this ETS, where a modem provides the facility to
signal from one V.22bis modem a rate change request either from 2 400 bit/s to 1 200 bit/s or vice versa
to a remote V.22bis modem by means of the temporary cessation of transmission in the data channel of
scrambled data and by its substitution by the transmission of special symbols, or to act upon such a
request, the operation of that facility shall be in accordance with the requirements of subclauses 5.8.4.1
and 5.8.4.2.
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Table 1: Coding of rate change dibits
Signal Dibit Operating Rate
R1 R2
11 11 2 400 bit/s
01 or 10 01 or 10 1 200 bit/s
5.8.4.1 2 400 bit/s to 1 200 bit/s
5.8.4.1.1 Instigation of a rate change
The rate change request shall be initiated by the modem indicating to the DTE that it is not ready to
transmit data (equivalent: turning OFF CcT 106) and transmitting Signal S1 (see clause 3) for 100 ms
± 3 ms. This shall then be followed by transmission of scrambled Signal R1 as defined in table 1, i.e.
alternating binary 1 and 0 at 1 200 bit/s for a minimum period of 687 ms.
- If Signal R2 from the remote modem indicates its disagreement, i.e. it responds with contiguous
binary 1, then scrambled Signal R1 shall be followed by scrambled binary 1 at 2 400 bit/s for
200 ms ± 10 ms;
- otherwise it shall be followed by scrambled binary 1 at 1 200 bit/s for 200 ms ± 10 ms.
At the end of this period, the modem shall indicate that it is ready to transmit data (equivalent: turning ON
CcT 106) and re-enter the data transfer phase at the agreed data rate.
Compliance shall be checked by the method described in annex A, subclause A.8.3.1.1.
5.8.4.1.2 Response to a request for rate change
On detection of Signal S1 during the data transmission phase, the modem shall give an indication to the
DTE that the modem is no longer able to transmit data (equivalent: turning OFF CcT 106), clamp the
received data to constant binary 1 (equivalent: clamping CcT 104 to constant binary 1), and respond by
transmitting Signal S1 for 100 ms ± 3 ms. This shall be followed by transmission of scrambled Signal R2
as defined in table 1 for a period such that the total period for S1 and R2 is 600 ms ± 10 ms and where R2
is either:
a) alternating binary 1 and 0 at 1 200 bit/s; or
b) binary 1 at 1 200 bits.
NOTE: Transmission of b) above indicates a refusal or an inability to change the signalling
rate.
This shall be followed by scrambled binary 1 at the rate indicated in R2 above.
At the end of this period, the modem gives an indication to the DTE that the modem is again ready to
transmit data (equivalent: turning ON CcT 106) and remove the clamp from the received data (equivalent:
output decoded data on CcT 104) and shall re-enter the data transfer phase at the agreed data rate.
For the purposes of test, the applicant shall indicate, what facilities, if any, could prevent a rate change.
Compliance shall be checked by the method described in annex A, subclause A.8.3.1.2.
5.8.4.2 1 200 bit/s to 2 400 bit/s
5.8.4.2.1 Instigation of a rate change
The rate change request shall be initiated by the modem indicating to the DTE that it is no longer ready to
transmit data (equivalent: turning OFF CcT 106) and transmitting Signal S1 for 100 ms ± 3 ms. This shall
then be followed by transmission of scrambled Signal R1 as def
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