ETSI ETS 300 114 ed.2 (1996-05)
Public Switched Telephone Network (PSTN); Basic Category I and Category II specifications for modems standardized for use on the PSTN
Public Switched Telephone Network (PSTN); Basic Category I and Category II specifications for modems standardized for use on the PSTN
RE/TE-05045
Javno komutirano telefonsko omrežje (PSTN) – Specifikacije osnovne kategorije I in kategorije II za modeme, standardizirane za uporabo v PSTN
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2003
Javno komutirano telefonsko omrežje (PSTN) – Specifikacije osnovne kategorije I
in kategorije II za modeme, standardizirane za uporabo v PSTN
Public Switched Telephone Network (PSTN); Basic Category I and Category II
specifications for modems standardized for use on the PSTN
Ta slovenski standard je istoveten z: ETS 300 114 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 300 114
TELECOMMUNICATION May 1996
STANDARD Second Edition
Source:ETSI TC-TE Reference:RE/TE-05045
ICS: 33.020
modem, PSTN, testing
Key words:
Public Switched Telephone Network (PSTN);
Basic Category I and Category II specifications
for 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 300 114: 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 300 114: May 1996
Contents
Foreword .7
1 Scope .9
2 Normative references.9
3 Definitions and abbreviations .11
3.1 Definitions .11
3.2 Abbreviations .12
4 Common requirements.13
4.1 General notes .13
4.2 PSTN access requirements.13
4.3 Information to be provided by the applicant.13
4.3.1 Information required for testing purposes .13
4.3.1.1 List of modes .13
4.3.1.2 Other items .13
4.3.2 Instructions for use.14
5 Requirements common to some Category II modems .14
5.1 General notes .14
5.2 Call establishment sequence based upon CCITT Recommendation V.25.14
5.2.1 For modems initiating calls.14
5.2.1.1 Calling tone generation.14
5.2.1.2 Answering tone detection .15
5.2.2 For modems answering calls .15
5.3 Test loop implementation based upon CCITT Recommendation V.54 .15
5.3.1 General.15
5.3.2 Remote digital test loop (loop 2).16
5.3.3 Local analogue test loop (loop 3) .16
5.4 Threshold of received line signal detection.16
5.5 Requirements for modems providing asynchronous to synchronous conversion based
upon CCITT Recommendation V.14 .17
5.5.1 General.17
5.5.2 Transmission of start-stop characters.17
5.5.2.1 Signalling rate ranges of the start-stop characters at the
modem input.17
5.5.2.2 Start-stop character format.17
5.5.2.3 Asynchronous to synchronous conversion .18
5.5.2.3.1 Transmitter.18
5.5.2.3.2 Receiver.18
5.5.2.3.3 Break signal .19
5.5.2.3.3.1 Transmitter.19
5.5.2.3.3.2 Receiver.19
5.6 Performance .19
5.6.1 Overall performance.19
5.6.2 Performance in the presence of metering pulses .19
Annex A (informative): Testing methods for national variants for clause 4.21
A.1 General notes.21
Annex B (normative): Testing methods for clause 5 .22
B.1 General conditions for test .22
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ETS 300 114: May 1996
B.2 Tests of the call establishment sequence specified in subclause 5.2 . 22
B.2.1 For modems initiating calls. 22
B.2.1.1 Calling tone. 22
B.2.1.2 Detection of answering tone . 23
B.2.2 For modems answering calls . 23
B.3 Tests to verify the test loop implementation specified in subclause 5.3. 23
B.4 Tests to verify the threshold of line signal detection. 23
B.5 Tests to verify the process of asynchronous to synchronous conversion specified in subclause
5.5. 24
B.5.1 Test patterns . 24
B.5.1.1 General . 24
B.5.1.2 Standard test text. 24
B.5.1.3 Discrete Test Characters (DTC). 25
B.5.2 Data signalling rates. 25
B.5.3 Tests . 26
B.5.3.1 Transmitter tests. 26
B.5.3.1.1 Omission of stop elements . 26
B.5.3.1.2 Over-speed and under-speed capabilities . 26
B.5.3.1.3 Arbitrary character spacing . 27
B.5.3.1.4 Break signal transmission. 28
B.5.3.2 Receiver tests. 28
B.5.3.2.1 Over-speed capability . 28
B.5.3.2.2 Under-speed capability . 29
B.5.3.2.3 Character recovery. 29
B.5.3.2.4 Break signal reception . 29
B.6 Performance testing methodology. 29
B.6.1 General. 29
B.6.2 Definitions. 30
B.6.3 Method of measurement . 31
B.6.3.1 Test set-up. 32
B.6.3.2 Test 1. 34
B.6.3.3 Test 2. 37
B.6.3.4 Test 3. 38
Annex C (normative): Description of specialised test facilities, specification of test lines for use in
assessing the performance of Category II modems. 39
C.1 General. 39
C.2 Test set-up. 39
C.2.1 Simulated PSTN conditions . 40
C.3 Test Line 1 transmission characteristics . 45
C.3.1 Local line simulators. 45
C.3.2 Trunk network simulator. 45
C.3.3 Permanent impairments. 46
C.3.3.1 Insertion loss. 46
C.3.3.2 White noise. 46
C.3.3.3 Frequency offset and Phase roll. 55
C.3.3.4 Phase jitter. 55
C.3.3.5 Echo. 55
C.3.3.6 Harmonic distortion. 55
C.4 Test Line 2 transmission characteristics . 55
C.4.1 Local line simulators. 55
C.4.2 Trunk network simulator. 63
C.4.3 Permanent impairments. 63
C.4.3.1 Insertion loss. 63
C.4.3.2 Frequency offset and phase roll . 63
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ETS 300 114: May 1996
C.4.3.3 Phase jitter .63
C.4.3.4 Echo .63
C.4.3.5 Harmonic distortion .64
C.4.3.6 Noise floor .64
C.5 Test Line 3 transmission characteristics .64
Annex D (normative): Provision of test tools .65
Annex E (informative): Example of proforma chart for information request.66
Annex F (informative): Bibliography.67
History.68
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ETS 300 114: 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).
This ETS is one of a series of ETSs which are applicable to modems. Details of the current series are
given in clause 2 of this ETS (Normative references, numbers [1] to [7] inclusive).
This second edition was produced in order to solve some technical errors and problems that were
reported on the first version, as well as to reflect the changed regulatory environment in relation to type
approval. Where the first edition of the document defines in detail Category I and II approvals concept (in
which only Category I approval was mandatory), this second edition still uses the Category I and II
terminology. However, these documents, unlike their predecessors, which were used as the basis of the
NETs 20 to 25, are not intended for regulatory application.
The regulatory approval of a modem does not require the modem to comply, for instance, with any of the
V.series of CCITT/ITU-T Recommendations, nor does it require the modem to function or perform as a
modem. An approved modem may or may not be in compliance with certain CCITT/ITU-T
Recommendations. However since this is not tested, no assurance of interworking is implied.
Conformity to a Category II specification, which is entirely voluntary and only applicable when the supplier
requests it, is only available to modems providing certain combinations of functionality based on the
modem specific V.series CCITT/ITU-T Recommendations. The object of this Category II specification is to
provide the user with the assurance that a modem can interwork, under most network conditions, with
other compatible Category II modems.
NOTE 1: However, as the PSTN is primarily engineered to convey speech traffic, connections
not permitting satisfactory data transmission can occur.
To be in conformance with the Category II specifications, and hence be called a “Category II modem” the
modem needs, in addition to meeting the appropriate approval requirements, to meet the requirements
given in one or more modem-specific ETS (final draft prETS 300 002 [6], ETS 300 115 [2] and final draft
prETSs 300 116 to 300 118 ([3] to [5])). Certain requirements common to more than one specific ETS are
included, for simplicity in clause 4 and annexes B, C and D, and are referred to (as required) in the
modem-specific ETSs. The degree of compliance required by these ETSs with any V. series of
CCITT/ITU-T Recommendation has been intentionally limited to that which might reasonably be
considered necessary in order to provide the intended assurance of inter-working between modems. In
particular, there is no requirement that the digital interface of the modem conform to any particular
physical realisation or functionality, and with certain identified exceptions, there are no requirements
relating to the digital interface.
For instance, the following types are examples of features which do not affect modem to modem
interworking and do not prevent the modem from being in conformance with the Category II specification,
as long as it meets the requirements of the appropriate modem-specific ETS:
- PC integral modems that present a bus interface;
- modems employing a proprietary auto-dialling protocol;
- "intelligent" modems that may send messages to a DTE;
- multi-mode modems that may connect to a variety of modem types.
Any modem that can be configured to meet the relevant requirements can potentially be found conforming
to this Category II specification and hence be considered as a “Category II modem” for that mode of
operation.
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ETS 300 114: May 1996
It is acceptable for a modem to be tested against Category II specifications in only some of its potential
operating modes. Where this is the case, it is necessary to, in other operating modes to be used on the
PSTN, meet the appropriate approval requirements. The "Instructions for Use" make it clear to the user
those modes which the modem has found to comply with the requirements for contained in the Category II
specification.
The requirements and the descriptions of the associated tests described in this ETS are specified to
provide correct inter-working with the PSTN, minimise the risk of hazardous electrical conditions
appearing on the PSTN, minimise the risk conditions occurring on the PSTN which might create hazards
for those using the modem and to ensure end-to-end interpretability between modems in compatible
configurations.
NOTE 2: Compliance with a modem specific ETS provides to the user an added degree of
assurance of interoperability over the PSTN. However, as the PSTN is primarily
engineered to convey speech traffic, connections not permitting satisfactory data
transmission can occur.
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 300 114: May 1996
1 Scope
This second edition European Telecommunication Standard (ETS) contains the technical characteristics
required for end-to-end interworking over the Public Switched Telephone Network (PSTN). Clauses of this
ETS also contain Category II specifications define for certain features which may be provided by some
modems, but the requirements in these parts are only applicable when invoked by a modem specific ETS.
The term "modem" in the context of this ETS includes all physical implementation practices for voice band
modems which are conductively connected to the PSTN.
NOTE: This implies that certain types of modems, e.g. acoustically coupled and cordless
modems, are outside the scope of this ETS.
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 for clause 4 is given in annex A (informative) and for clause 5 in annex B (normative).
Annex C (normative) describes the testing facilities which a testing laboratory may need to provide.
Annex D (normative) indicates additional equipment, or software, that applicants may need to provide in
order that testing to Category II can be achieved.
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 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] ETS 300 001: "Attachments to Public Switched Telephone Network (PSTN);
General technical requirements for equipment connected to an analogue
subscriber interface in the PSTN".
[2] ETS 300 115 (1991): "Attachments to the Public Switched Telephone Network
(PSTN); Category II attachment requirements for 300 bits per second duplex
modems standardized for use on the PSTN [Candidate NET 21]".
[3] Final draft prETS 300 116 (1996): "Public Switched Telephone Network (PSTN);
Category II specification for 1 200 bits per second duplex modems standardized
for use on the PSTN".
[4] Final draft prETS 300 117 (1996): "Public Switched Telephone Network (PSTN);
Category II specification for 2 400 bits per second duplex modems standardized
for use on the PSTN".
[5] Final draft prETS 300 118 (1996): "Public Switched Telephone Network (PSTN);
Category II specification for 1 200 bits per second half-duplex and 1 200/75 bits
per second asymmetrical duplex modems standardized for use on the PSTN".
[6] Final draft prETS 300 002 (1996): "Public Switched Telephone Network (PSTN);
Category II specification for 9 600 or 4 800 bits per second duplex modems
standardized for use on the PSTN".
[7] Final draft prETS 300 492 (1996): "Public Switched Telephone Network (PSTN);
Category II specification for 14 400, 12 000, 9 600, 7 200 and 4 800 bits per
second duplex modems standardized for use on the PSTN".
[8] CCITT Recommendation V.24 (1984): "List of definitions for interchange circuits
between Data Terminal Equipment and Data Circuit-Terminating Equipment".
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ETS 300 114: May 1996
[9] CCITT Recommendation V.14 (1988): "Transmission of start-stop characters
over synchronous bearer channels".
[10] CCITT Recommendation V.25 (1984): "Automatic answering equipment and/or
parallel automatic calling equipment on the general switched telephone network
including procedures for the disabling of echo control devices for both manually
and automatically established calls".
[11] CCITT Recommendation V.21 (1984): "300 bits per second duplex modem
standardized for use in the General Switched Telephone Network".
[12] CCITT Recommendation V.54 (1984): "Loop test devices for modems".
[13] CCITT Recommendation V.4 (1984): "General structure of signals of
international alphabet No. 5 code for data transmission over public telephone
networks".
[14] 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".
[15] CCITT Recommendation V.52 (1984): "Characteristics of distortion and error-
rate measuring apparatus for data transmission".
[16] CCITT Recommendation V.22 (1984): "1200 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".
[17] CCITT Recommendation V.22bis (1988): "2400 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".
[18] CCITT Recommendation V.23 (1984): "600/1200-baud modem standardized for
use in the General Switched Telephone Network".
[19] CCITT Recommendation V.32 (1984): "A family of 2-wire, duplex modems
operating at data signalling rates up to 9600 bits/s for use on the general
switched telephone network and on leased telephone type circuits".
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ETS 300 114: May 1996
3 Definitions and abbreviations
3.1 Definitions
For the purposes of this and other related ETSs, the following definitions apply:
answer mode: When calls are established with automatic facilities, a standard answer mode is 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 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 is necessary.
built-in modem: A functionally separate internal modem which is mechanically combined with a terminal.
call mode: When calls are established with automatic facilities, a standard call mode is 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, a bilateral agreement on
the use of call mode and answer mode is 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
suitable device may monitor or generate such signals.
integrated modem: An internal modem which is functionally and physically merged with the terminal.
internal modem: A modem which is physically incorporated in a terminal equipment and which takes its
electrical power supply from the terminal.
Different types of internal modems are defined: built-in, plug-in and integrated modems.
intra-character signalling rate: The intra-character signalling rate of a message is the signalling rate of
the start element and data elements within each character of this message.
modem: A functional unit that modulates and de-modulates signals in order to enable digital data to be
transmitted over analogue transmission facilities.
modem used for reference: A modem used for some of the tests specified herein or in a 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 is 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 [8]).
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 a modem specific ETS, that have an influence upon line signals
present at the PSTN interface.
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ETS 300 114: May 1996
modes of use: Modes specified in a modem specific ETS, that have an influence upon conditions present
at a digital interface e.g. a "conventional" CCITT Recommendation V.24 [8] interface or a PC bus interface
in the case of an integrated modem.
on-line state: 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 the on-line condition is potentially capable of sending or receiving
speech-band information to or from the network.
plug-in modem: A physically and functionally separate internal modem which is interchangeable from a
terminal.
round trip delay: This is twice the time taken for a transmitted signal to be propagated to the far end of a
telephone connection.
For all tests where adherence to CCITT Recommendations is being checked the requirement and test
assume a round trip delay of 0 ms. The round trip delay of the test line (test line 3) being used for the tests
should be determined and the results of measurement adjusted by subtracting either half the round trip
delay or the round trip delay as appropriate from the value obtained before comparing it with the pass/fail
limit given in this ETS.
silence: This term is used to describe periods during the hand-shaking sequences where signals are not
transmitted.
The period of silence is measured using the start and finish criteria defined below. The levels refer to
signals which in the relevant frequency band have an in-band power level and are expressed with respect
to the normal transmitted signal level of the modem under test recorded at the point of observation.
The start of the period of silence is defined as the instant at which the transmitted signal level drops below
a level that is 6 dB below the normal transmit level.
The period of silence ends the instant the transmitted signal rises above a level that is 6 dB below the
normal transmit level. During the period of silence at least one instant is observed where the signal level is
at least 30 dB below the normal transmit level.
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
NEL Nominal Element Length
PSTN Public Switched Telephone Network
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4 Common requirements
4.1 General notes
This clause specifies the requirements to be met by all modems seeking conformance with Category I or
Category II specifications.
4.2 PSTN access requirements
The requirements of ETS 300 001 [1] apply.
4.3 Information to be provided by the applicant
4.3.1 Information required for testing purposes
The applicant shall provide to the testing authority, at least the information indicated below:
- equipment nature (stand-alone, rack-mounted, integrated in a terminal);
- intended category (Category I and/or Category II);
- countries for which the equipment is intended for attachment.
An example proforma chart to collect this information is provided in annex E.
4.3.1.1 List of modes
The applicant shall specify those modes of the equipment relevant to operation on the PSTN and for
which of them assessment of conformance is sought, and which of them are intended for use in specified
countries:
- list of carrier modes;
- automatic answering;
- automatic calling;
- provision of line loop 3 during a connection;
- special features.
4.3.1.2 Other items
The applicant shall provide the following information:
- additional technical information (transmitted level, minimum received level.);
- power supply;
- environmental characteristics.
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ETS 300 114: May 1996
4.3.2 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) the modes for which only the Category I conformance has been assessed;
c) any information specifically indicated in this ETS for inclusion in the "Instructions for use";
d) 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 Requirements common to some Category II modems
5.1 General notes
This clause contains requirements which are common to some of the following modem specific ETSs and
could be invoked by:
- ETS 300 115 [2];
- final draft prETS 300 116 [3];
- final draft prETS 300 117 [4];
- final draft prETS 300 118 [5];
- final draft prETS 300 002 [6];
- final draft prETS 300 492 [7].
On the whole, these requirements are based upon, and do not conflict with, CCITT/ITU-T
Recommendations, nevertheless some exceptions have been introduced in subclause 5.5 (for
asynchronous to synchronous conversion based upon CCITT Recommendation V.14 [9]) and in
subclause 5.6 (for modem performance tests).
NOTE: In the following, references are made to interchange circuits between the modem and
the DTE, as defined in CCITT Recommendation V.24 [8]. DTEs using certain
customized modems should not generally provide an interface with such interchange
circuits. For these cases the references to CCITT Recommendation V.24 [8] type
interchange circuits indicate equivalent operation of a DTE and of a modem where this
exists.
5.2 Call establishment sequence based upon CCITT Recommendation V.25
5.2.1 For modems initiating calls
The requirements of this subclause shall only be mandatory when invoked by a requirement in the
relevant specific ETS.
5.2.1.1 Calling tone generation
The provision of a calling tone as described in CCITT Recommendation V.25 [10] is optional. Where this
facility has been provided the calling tone shall be 1 300 Hz with the exception of CCITT Recommendation
V.21 [11] modems where it shall be either 980 Hz or 1 300 Hz. Multi-mode modems providing this facility
shall use 1 300 Hz.
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ETS 300 114: May 1996
Compliance shall be checked by the method described in annex B, subclause B.2.1.1.
5.2.1.2 Answering tone detection
After completion of the dialling phase, when the calling modem or its associated automatic call
establishment equipment is presented with valid answer tone in the range 2 078 Hz to 2 122 Hz indicating
that the remote modem has connected to line, the modem shall not give an indication to the DTE that it is
ready to operate (equivalent: turning ON Cct 107) until a single interruption of at least 55 ms has been
detected in answer tone or until a valid carrier signal has been detected.
NOTE 1: Since not all modems respond with answer tone, it is strongly recommended that
Category II modems are also capable of connecting to line on receipt of a valid carrier.
The exact timing of the indication in relation to the break in answer tone is a function of the specific type of
modem in use. For example, inter-working would not be adversely affected if such an indication was
delayed until after the receipt of valid carrier.
The behaviour of the modem, when presented with tones which are not valid answer tones is not tested.
NOTE 2: These requirements are derived from subclauses 3.18 to 3.20 of CCITT
Recommendation V.25 [10]; the calling tone and calling station response, if present,
should only be constrained by ETS 300 001 [1].
Compliance shall be checked by the method described in annex B, subclause B.2.1.2.
5.2.2 For modems answering calls
The requirements of this subclause shall only be mandatory when invoked by a requirement in the
relevant specific ETS.
Following establishment of on-line conditions, the modem shall remain silent for a period not less than
1,8 s. The modem, or its associated automatic answering equipment, shall then transmit 2 100 Hz ±
15 Hz. In the case where the calling station response is not present, the duration of this tone shall be 3,3 s
± 0,7 s. This shall be followed by a silent period, the duration of which is 75 ms ± 20 ms after which an
indication shall be given to the DTE that the modem is ready to operate (equivalent: turning ON Cct 107).
NOTE 1: This requirement is derived from subclauses 4.3 & 4.4 of CCITT Recommendation
V.25 [10].
NOTE 2: The level at which the tone is transmitted is constrained by ETS 300 001 [1].
NOTE 3: The answering sequence described above has the effect of disabling network echo
suppressors where present. Modems requiring to disable network echo cancellers as
well as network echo suppressors, are advised to transmit 180° phase reversals in the
2 100 Hz tone at 450 ms ± 25 ms intervals.
NOTE 4: An upper limit for the silent period is not specified, so as not to preclude a modem from
providing detection facilities that would identify particular types of calling device.
NOTE 5: The exact timing of the indication that the modem is ready to operate (equivalent:
turning ON Cct 107) is a function of the specific type of modem in use.
Compliance shall be checked by the method described in annex B, subclause B.2.2.
5.3 Test loop implementation based upon CCITT Recommendation V.54
5.3.1 General
This describes the test loop functions which may be provided in modems.
The method of initiating such loops (e.g. manually, locally or remotely) is described in the appropriate
ETS.
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ETS 300 114: May 1996
Figure 1 roughly indicates the function of these test loops.
LOOP 3
MOD
TO
DTE
LOOP 2
DEMOD
PSTN
Figure 1: Test loops
5.3.2 Remote digital test loop (loop 2)
This test loop may be used for a basic test of the local modem, the network connection and the remote
modem. This loop is only of practical use with full duplex modems. Once instigated, this loop causes data
transmitted by the DTE to be returned back on the received data connection through the remote modem.
5.3.3 Local analogue test loop (loop 3)
This test loop may be used to establish that the local modem is functioning correctly. The implementation
of this loop should ensure, that in so far as is possible, all the circuitry within the modem used for
processing the signals is included in the test.
5.4 Threshold of received line signal detection
The requirements of this subclause are only mandatory when invoked by a requirement in the relevant
specific ETS.
All levels shall be determined with the modem replaced by a 600 ohm non-reactive resistor.
When a valid line signal, as described in the relevant modem specific ETS, is applied to the line terminals
of a modem at any level above - 43 dBm, the modem shall be capable of establishing a data connection
and passing data to a DTE, to which the modem shall give an appropriate indication (e.g. equivalent to
turning CcT 109 ON).
When a modem is presented with a valid line signal at a level below - 48 dBm the modem shall not
establish a data connection (i.e. pass data derived from the line signal) to a DTE, to which the modem
shall give an appropriate indication (e.g. equivalent to CcT 109 remaining OFF).
The lowest level at which, for a valid line signal, the modem indicates to the DTE the capability of
establishing a data connection, or of passing data, shall be at least 2 dB greater than the level at which it
indicates to the DTE that the capability to continue to pass data over the established connection has
ceased (e.g. equivalent to turning CcT 109 OFF).
Compliance shall be checked by the method described in annex B, clause B.4.
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ETS 300 114: May 1996
5.5 Requirements for modems providing asynchronous to synchronous conversion based
upon CCITT Recommendation V.14
5.5.1 General
This subclause defines the requirements for a Category II modem providing facilities for the conversion of
asynchronous transmission to synchronous transmission without any error correction, speed conversion
or flow control process. The requirements of this subclause shall only be mandatory if they are referenced
by another ETS.
To comply with the requirements of subclause 5.5.2, it is necessary that the modem provide transmission
of start-stop characters in at least one of the following character 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.
NOTE 1: The following requirements are derived from CCITT Recommendation V.14 [9]. If an
error correction function is to be included in the modem, asynchronous to synchronous
conversion as described in CCITT Recommendation V.42 (1988) should be used.
NOTE 2: For integrated modems, some of the requirements cannot be verified and therefore are
the subject of an applicant's declaration of conformance.
5.5.2 Transmission of start-stop characters
5.5.2.1 Signalling rate ranges of the start-stop characters at the modem input
The process of asynchronous to synchronous conversion within the modem shall be capable of receiving
characters from a DTE whose speed varies by + 1 % to - 2,5 % (referred to hereinafter as the basic rate
range) from the nominal data signalling rate without any corruption of data.
Optionally, the modem may also be capable of receiving characters from a DTE whose speed varies by
+ 2,3 % to - 2,5 % (referred to hereinafter as the extended rate range) from the nominal data signalling
rate without any corruption of data.
5.5.2.2 Start-stop character format
It shall be possible to configure the conversion process within the modem to accept one or more of the
following formats:
a) a one-unit start element, followed by six data units, and a one-unit stop element (8-bit characters);
b) a one-unit start element, followed by seven data units, and a one-unit stop element (9-bit
characters);
c) a one-unit start element, followed by eight data units, and a one-unit stop element (10-bit
characters);
d) a one-unit start element, followed by nine data units, and a one-unit stop element (11-bit
characters).
It shall be possible to transmit characters continuously or with any additional stop elements of arbitrary
length between characters.
The character format selected shall be the same for both the transmitter and the receiver of the modem.
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ETS 300 114: May 1996
NOTE 1: It is assumed that characters presented to the modem are in accordance with CCITT
Recommendation V.4 [13]. Character formats a) and d) do not conform to the
International Alphabet No. 5.
NOTE 2: In each of the four formats, data units can be replaced by additional stop units. For
example, format d) will allow 11-bit characters consisting of a one-unit start element,
followed by eight data units and a stop element of two units to be handled.
5.5.2.3 Asynchronous to synchronous conversion
The method of handling the speed differences between the intra-
...
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