ETSI ETS 300 115 ed.1 (1991-06)

SLOVENSKI STANDARD
01-december-2003
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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)
Ta slovenski standard je istoveten z: ETS 300 115 Edition 1
ICS:
33.040.35 Telefonska omrežja Telephone networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 115
TELECOMMUNICATION June 1991
STANDARD
Source: Reference:
ICS:33.020
PSTN, 300 bits/second duplex modems
Key words:
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
(The text of this ETS may be utilized, wholly or in part,
for the establishment of NET 21)
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 1991. All rights reserved.
New presentation - see History box

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ETS 300 115: June 1991
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Standards Approval Dept." at the address shown on the title page.

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ETS 300 115: June 1991
Contents
Foreword.5
1 Scope .7
2 Normative References .7
3 Definitions and abbreviations.7
3.1 Definitions.7
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.9
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. 10
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 (RFS) indicator. 12
5.6 Threshold of the received line signal detector . 13
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

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ETS 300 115: June 1991
A.6 Test for subclause 5.9.1 (Distortion) .17
A.6.1 Compliance with subclause a) . 17
A.6.2 Compliance with subclause b) .17
A.6.3 Compliance with subclause c).18
Annex B (Informative): 300 bits per second modem based on Recommendation CCITT V.21 [4].19
History .20

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ETS 300 115: June 1991
Foreword
This European Telecommunication Standard (ETS) has been produced by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI). The text of this ETS
may be utilized, wholly or in part, for the establishment of NET 21.
This ETS contains the technical requirements for approval to Category II of 300 bits per second duplex
modems standardised for use on the Public Switched Telephone Network (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 have been inserted to assist inter-operability.
Additionally, requirements are included which relate to end-to-end inter-operability over PSTN connections.
These requirements are in excess of the CCITT Recommendations. 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 ETS 300 114 [2], Clause 4.
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,
etc.
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ETS 300 115: June 1991
1 Scope
This ETS specifies the technical characteristics to be offered by modems seeking Category II approval for
duplex operation over the PSTN at 300 bits per second. The modulation scheme specified is that described
in CCITT Recommendation V.21 [4].
The term "modem" in the context of this ETS includes all physical implementation practices for voice band
modems which are galvanically 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 (Normative).
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] Draft prETS 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 and Data Circuit-Terminating Equipment"
[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"
3 Definitions and abbreviations
The definitions and abbreviations of ETS 300 114 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

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ETS 300 115: June 1991
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 shall be necessary.
Call mode: When calls are established with automatic facilities, a standard call mode shall be used by the
modem at the calling station. This mode consists of conventional characteristics (e.g. use of low channel
carrier frequency or particular scrambler generating polynomial) complementary to those used in the
standard answer mode by the modem at the answering station, in order to ensure proper connection and
inter-working.
If calls are established on the PSTN by operators, or for leased line operation, bilateral agreement on the
use of call mode and answer mode shall be necessary.
Data Terminal Equipment (DTE): 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 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.
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 himself. 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;

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ETS 300 115: June 1991
- 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
AMM Answer Mode Modem
CCITT Comité Consultatif International Télégraphique et Téléphonique
Cct Circuit
CEPT Conférence des Administrations Européennes des Postes et des
Télécommunications
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 Draft prETS 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 which of the modes of operation/use identified in this ETS approval to Category
II is sought.
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:

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ETS 300 115: June 1991
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 subject of another ETS.
Compliance shall be checked by inspection.
5 Functional requirements specific to Category II modems
5.1 General requirements
To comply with the requirements of this ETS, it shall be necessary that the modem provide:
- duplex mode of operation 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, Definitions);
- where a modem is capable of transmitting in 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 customised 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 approval for
Category II is sought. An example of a proforma which requests the relevant information is attached at
Appendix B (Informative).
5.3 Line signals
The modem transmits on the low channel when receiving on the high channel, and vice versa, according to
the channel allocation requirements defined in subclause 5.4.
Note: The channels are referred to in CCITT Recommendation V.21 [4] as channel 1 and
channel 2. In order to retain a common presentation within this series of ETSs, this
ETS refers to channel 1 as the low channel and channel 2 as the high channel.
5.3.1 Carrier frequencies
The characteristic frequencies Fa and Fz as measured at the line terminals of the modem, shall not deviate
by more than ± 2 Hz from those given in Table 1.

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ETS 300 115: June 1991
Table 1: Frequency Allocation
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”       ‡   Binary 0 (Fa)  ‡   Binary 1 (Fz) ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¶
” Low Channel ‡    1180 Hz    ‡     980 Hz   ”
˙˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¶
” High Channel‡    1850 Hz    ‡    1650 Hz   ”
¨˝˝˝˝˝˝˝˝˝˝˝˝˝ˇ˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝ˇ˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝˝…
Compliance shall be checked by the method described in Annex A, Clause A.
...