SIST ETS 300 115 E2:2003

• Abstract:

  This ETS specifies the technical characteristics required for end-to-end interworking over the PSTN of 300 bit/s modems standardized for use over the PSTN in accordance with ITU.T Rec V.21. New Work Item supported by Belgacom, BT, Deutsche Telekom and Austrian PTT.

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.040.35 - Telephone networks
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI ETS 300 115 ed.2 (1997-09) - Public Switched Telephone Network (PSTN); Category II specification for 300 bit/s duplex modems standardized for use on the PSTN

SIST ETS 300 115 E2:2003 is the Slovenian adoption of ETS 300 115 Edition 2 from ETSI. It specifies the technical characteristics for end-to-end interworking over the Public Switched Telephone Network (PSTN) of 300 bit/s duplex modems standardized for use on the PSTN in accordance with CCITT Recommendation V.21. The document is used when a supplier, applicant, or test laboratory needs to check Category II modem behaviour and interoperability.

What does SIST ETS 300 115 E2:2003 specify?

SIST ETS 300 115 E2:2003 specifies the PSTN-facing requirements for 300 bit/s duplex modems, including the operating modes, line signals, timing, performance, and the test methods used to verify them. It is organized into scope, normative references, definitions and abbreviations, general requirements, functional requirements for Category II modems, and two annexes.

Annex	What it covers
Annex A	Normative testing methods, test conditions, and the procedures used to check compliance with the functional requirements
Annex B	Informative declaration form for the modem modes of operation/use and auto-calling or auto-answering facilities

The scope focuses on conductively connected voice-band modems on the PSTN. The document also states that the modem may operate in answer mode, call mode, or both, depending on the product and the applicant’s declared modes for testing.

What are the key requirements of SIST ETS 300 115 E2:2003?

SIST ETS 300 115 E2:2003 combines general attachment requirements from ETS 300 114 with modem-specific requirements for Category II operation. For a reader deciding whether a modem fits this standard, the practical points are the channel plan, the timing of signals, and the test results the modem must achieve.

General attachment and applicant information

Clause 4 requires the modem to comply with ETS 300 114 clause 4. The applicant must declare which modes of operation or use are to be tested, and the instructions for use must identify the apparatus, include any information required by the ETS, and state any national restrictions. In practice, this means the product file needs clear mode declarations and user documentation before assessment begins.

Core modem functions

Clause 5.1 requires duplex operation with continuous carrier, frequency division channel separation, frequency shift binary modulation, line signalling rates up to 300 bit/s, and initial carrier mode. If the modem can transmit on either channel, it must provide means to select the channel manually and/or automatically. This matters because the modem must always present the expected V.21-style call and answer behaviour on the PSTN.

Operating modes and channel allocation

Clause 5.2 requires the modem to be configurable in at least one of two modes: answer mode or call mode. Clause 5.4 then assigns the channels: a Call Mode Modem (CMM) transmits on the low channel and responds on the high channel, while an Answer Mode Modem (AMM) does the opposite. If the modem can work as both, it must support at least one of three selection methods - manual selection, selection by the DTE, or automatic selection. In practice, the test lab checks that the modem uses the correct channel for the call direction and does not transmit on both channel bands at once.

Carrier frequencies and spectral limits

Clause 5.3.1 sets the carrier frequencies for the binary 0 and binary 1 signals, with a tolerance of ±2 Hz from the specified values. Clause 5.3.2 sends spectral power control back to ETS 300 114. This means the modem’s transmitted tones must fall in a very narrow frequency window, so interoperability depends on accurate oscillator and modulation design.

Timing of detection and ready indication

Clause 5.5 defines the response times of the received line signal detector and the Ready For Sending (RFS) indicator. The detector must respond quickly enough when a carrier appears or disappears, and the RFS signal must follow carrier detection within a limited time window. In practice, these timings prevent call setup delays from causing data loss or dead time during handover between stations.

Auto-calling, auto-answering, looping, and performance

Clause 5.7 links auto-calling and auto-answering to the tone-detection and tone-generation requirements in ETS 300 114. Clause 5.8 says loop test facilities are not required, although their presence is allowed. Clause 5.9 adds performance checks: synchronous start-stop distortion is limited under three test-line conditions, and receiver performance must reach at least 90% error free seconds during the specified testing periods. For users, this means the modem must not only signal correctly, but also carry data reliably under the test conditions used for Category II assessment.

What terms does SIST ETS 300 115 E2:2003 define?

SIST ETS 300 115 E2:2003 uses a small set of terms that matter directly to modem operation and testing.

• Answer mode - The mode used by the answering station, with characteristics complementary to call mode so the two modems can interwork correctly.
• Call mode - The mode used by the calling station, complementary to answer mode.
• Data Terminal Equipment (DTE) - The digital equipment at the modem interface that sends or receives the data signals; a tester can stand in for it.
• Modem used for reference - The comparison modem used in some tests, supplied by the applicant or the testing authority.
• Initial carrier mode - The mode where the AMM transmits carrier immediately after auto answer, while the CMM waits until it detects carrier.
• On-line state - The electrical state in which the modem draws enough current to activate the exchange and can communicate over the network.
• Ready For Sending (RFS) - The indicator that tells the DTE the modem is ready to transmit data.
• Public Switched Telephone Network (PSTN) - The switched telephone network over which the modems are intended to interwork.

Who uses SIST ETS 300 115 E2:2003?

SIST ETS 300 115 E2:2003 is used by modem designers, manufacturers, and suppliers who need to build 300 bit/s PSTN modems to a defined behaviour. It is also used by applicants submitting equipment for conformance assessment, by testing laboratories, and by testing authorities that run the Annex A procedures.

Quality managers and buyers use it to check whether a modem supports answer mode, call mode, channel selection, and the test conditions needed for Category II assessment. Telecom engineers use it to compare modem behaviour against the expected V.21-based PSTN operation.

What changed in SIST ETS 300 115 E2:2003 from the previous edition?

SIST ETS 300 115 E2:2003 is the second edition of ETS 300 115. The document history shows a first edition from June 1991 and a second edition from September 1997.

Which standards are used with SIST ETS 300 115 E2:2003?

SIST ETS 300 115 E2:2003 relies on several named standards and recommendations for common requirements, definitions, and tests.

Reference	What it contributes
ETS 300 001	General technical requirements for equipment connected to an analogue subscriber interface in the PSTN
ETS 300 114	Basic attachment requirements for modems on the PSTN, plus the common requirements, definitions, and test conditions used by this ETS
CCITT Recommendation S.33	The test signals used for channel allocation testing
CCITT Recommendation V.21	The base 300 bit/s duplex modem recommendation that this ETS builds on
CCITT Recommendation V.24	Definitions of interchange circuits between DTE and DCE, used as equivalent control and status signals
CCITT Recommendation V.25	Automatic answering and automatic calling equipment requirements, including answering tone rules
CCITT Recommendation V.54	Loop test device definitions for modems

What does the SIST ETS 300 115 E2:2003 document contain?

SIST ETS 300 115 E2:2003 contains both requirements and the procedures to verify them. Annex A gives the test conditions and the methods for carrier frequency checks, channel allocation, response times, detector threshold, and distortion performance, using Test Line 1, Test Line 2, and Test Line 3 as needed. It also defines the one-minute cyclic discrete test character pattern used for the distortion tests.

Annex B provides an informative declaration format for the modem’s modes of operation and auto-calling or auto-answering facilities. The body of the document also includes the frequency allocation table, response-time tables, and the clauses that tie the modem’s operation to ETS 300 114 and the referenced CCITT Recommendations.

SLOVENSKI STANDARD
01-december-2003
Javno komutirano telefonsko omrežje (PSTN) - Specifikacija II. kategorije za
dupleksne modeme s hitrostjo 300 bit/s, standardizirane za uporabo v omrežjih
PSTN
Public Switched Telephone Network (PSTN); Category II specification for 300 bit/s
duplex modems standardized for use on the PSTN
Ta slovenski standard je istoveten z: ETS 300 115 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 300 115
TELECOMMUNICATION September 1997
STANDARD Second Edition
Source: ATA Reference: RE/ATA-005069
ICS: 33.020
Key words: Modems, PSTN, testing
Public Switched Telephone Network (PSTN);
Category II specification for 300 bit/s duplex modems
standardized for use on the PSTN
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
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 1997. All rights reserved.

Page 2
ETS 300 115: September 1997
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.

Page 3
ETS 300 115: September 1997
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions and abbreviations .8
3.1 Definitions .8
3.2 Abbreviations .9
4 General requirements .9
4.1 References to other ETSs .9
4.2 Information to be provided by the applicant.9
4.2.1 Information required for testing purposes .9
4.2.2 Instructions for use.10
5 Functional requirements specific to Category II modems .10
5.1 General requirements .10
5.2 Modes .10
5.3 Line signals.10
5.3.1 Carrier frequencies.11
5.3.2 Spectral power .11
5.4 Channel allocation .11
5.4.1 Channel selection.11
5.4.2 Automatic channel selection.11
5.5 Response times .12
5.5.1 Response times of the received line signal detector.12
5.5.2 Response times of the Ready For Sending indicator.12
5.6 Threshold of the received line signal detector .12
5.7 Provision of auto-calling and/or answering facilities (hand-shaking facilities) .13
5.7.1 Auto-calling - calling tone .13
5.7.2 Auto-calling - recognition of answering tone .13
5.7.3 Auto-answering .13
5.8 Provision of test looping facilities.13
5.9 Performance .13
5.9.1 Distortion .13
5.9.2 Receiver performance.14
Annex A (normative): Testing methods.15
A.1 General testing conditions.15
A.2 Test for subclause 5.3.1 (carrier frequencies) .15
A.3 Test for subclause 5.4 (channel allocation).15
A.3.1 Test for subclause 5.4.1 (channel selection) .15
A.3.2 Test for subclause 5.4.2 (automatic channel selection) .16
A.4 Compliance with subclause 5.5 (response times).16
A.4.1 Compliance with subclause 5.5.1 (Received Line Signal Detector) .16
A.4.2 Compliance with subclause 5.5.2 (RFS Indicator).17
A.5 Test for subclause 5.6 (Threshold of received line signal detector).17
A.6 Test for subclause 5.9.1 (Distortion) .17
A.6.1 Compliance with subclause(5.9.1 a).17

Page 4
ETS 300 115: September 1997
A.6.2 Compliance with subclause(5.9.1 b) . 18
A.6.3 Compliance with subclause(5.9.1 c) . 18
Annex B (informative): 300 bits per second modem based on CCITT Recommendation V.21. 19
History. 20

Page 5
ETS 300 115: September 1997
Foreword
This second edition European Telecommunication Standard (ETS) has been produced by ETSI Project
Analogue Terminals and Access.
The objective of this ETS, the application of which is entirely voluntary, is to provide users with an added
degree of assurance that modems in compliance with this ETS can interwork with each other, under most
network conditions.
This ETS contains the technical requirements required for end-to-end interworking over the Public
Switched Telephone Network (PSTN), 300 bits per second duplex modems standardized for use over the
PSTN.
These requirements are based upon, and do not conflict with, CCITT Recommendation V.21 [4] except in
the cases of subclause 5.3.1 where the frequency tolerances specified are tighter than those given;
subclause 5.5.1 (Response times of the received line signal detector) and subclause 5.5.2 (Response
times of the ready for sending indicator) where a restricted range of values has been inserted to assist
inter-operability. Additionally, requirements are included which relate to end-to-end interoperability over
PSTN connections. These requirements are in excess of the CCITT Recommendations.
Except where otherwise stated, a modem which complies with CCITT Recommendation V.21 [4] should
always meet the requirements of this ETS which relate to parameters specified in that CCITT
Recommendation except in the case of some of the intentional deviations identified above.
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 ETS 300 114 [2]. The definition of 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 300 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.
Transposition dates
Date of adoption: 19 September 1997
Date of latest announcement of this ETS (doa): 31 December 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 June 1998
Date of withdrawal of any conflicting National Standard (dow): 30 June 1998

Page 6
ETS 300 115: September 1997
Blank page
Page 7
ETS 300 115: September 1997
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) of
300 bits per second (bit/s) duplex modems standardized for use over the PSTN, in accordance with
CCITT Recommendation V.21 [4].
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 two modes of operation: answer mode and call mode.
NOTE: Modems can provide either simply one of the above modes or provide both modes
together with facilities for selecting either of the two modes.
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] 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 300 114 (1990): "Attachments to the Public Switched Telephone Network
(PSTN); Basic attachment requirements for modems standardized for use on
the PSTN".
[3] 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".
[4] CCITT Recommendation V.21 (1984): "300 bits per second duplex modem
standardized for use on the General Switched Telephone Network".
[5] CCITT Recommendation V.24 (1984): "List of definitions for interchange circuits
between Data Terminal Equipment (DTE) and Data Circuit Terminating
Equipment (DCE)".
[6] 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".
[7] CCITT Recommendation V.54 (1984): "Loop Test devices for modems".

Page 8
ETS 300 115: September 1997
3 Definitions and abbreviations
For the purposes of this ETS, the definitions and abbreviations of ETS 300 114 [2] apply, together with the
following:
3.1 Definitions
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 in the standard call mode by the modem at the calling station, in order to ensure proper connection
and interworking.
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
interworking.
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): This term 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.
degree of start-stop distortion: In start-stop transmission it is the ratio of the maximum measured
difference, irrespective of sign, between the actual and theoretical intervals separating any significant
instant from the significant instant of the start element immediately preceding it, to the unit interval.
The highest absolute value of degrees of individual distortion of the significant instants of a stop-start
signal is reached within a specific time interval.
The degree of distortion of start-stop modulation, restitution or signal shall be expressed as a percentage.
The result of measurement shall be completed by an indication of the period of the observation. The
start-stop distortion shall be considered positive when the significant instant occurs after the ideal instant
and conversely, negative when it occurs before.
degree of synchronous start-stop distortion: The degree of start-stop distortion determined when the
assumed unit interval is that appropriate to the actual modulation rate.
The degree of synchronous start-stop distortion shall be measured by adjusting the scanning rate of the
distortion measuring set.
The start-stop distortion shall be considered positive when the significant instant occurs after the ideal
instant and conversely, negative when it occurs before.
For the determination of the actual mean modulation rate, account shall only be taken of those significant
instants of modulation (or restitution) that correspond to a change on the same sense as that occurring at
the beginning of the start element.
initial carrier mode: A mode in which the Answer Mode Modem (AMM) transmits its carrier signal
immediately after the end of the auto answer sequence, and the Call Mode Modem (CMM) remains silent
until it receives a carrier signal from the AMM.

Page 9
ETS 300 115: September 1997
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 another modem
specific ETS. A modem used for reference may, at the discretion of the applicant, be provided by the
testing authority or by the applicant. It shall be designed:
- to meet the requirements of the same Recommendation(s) of the CCITT 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 [5]).
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 e.g. a "conventional" CCITT Recommendation V.24 [5] interface or a PC bus
interface in the case of an integral 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 state is potentially capable of sending or receiving
speech-band information to or from the network.
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
PSTN Public Switched Telephone Network
RFS Ready For Sending
4 General requirements
4.1 References to other ETSs
The modem shall comply with ETS 300 114 [2], clause 4.
NOTE: ETS 300 114 [2] 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 the modem is
required to undergo tests.
Page 10
ETS 300 115: September 1997
Compliance shall be considered to have been accomplished by provision of the relevant information.
NOTE: This could be accomplished by completion of a form such as the one 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
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:
- duplex mode of operation with continuous carrier, as specified in CCITT Recommendation V.21 [4];
- channel separation by frequency division;
- frequency shift binary modulation;
- line signalling rates of up to 300 bit/s;
- initial carrier mode (see subclause 3.1);
- where a modem is capable of transmitting on either of the two channels, means by which the
channels may be selected either manually and/or automatically.
In the following, references are made to interchange circuits between the modem and the DTE, as defined
in CCITT Recommendation V.24 [5]. 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 [5] type interchange circuits indicate equivalent functionality of a DTE and a
modem.
5.2 Modes
It shall be possible to configure the modem to operate in at least one of the following modes of operation:
- provision for transmission in the answer mode;
- provision for transmission in the call mode.
It shall be the applicant's responsibility to specify for which of these modes of operation, testing for
conformance to this ETS is required. An example of a proforma which requests the relevant informa
...