SIST ETS 300 114 E1:2003

SLOVENSKI STANDARD
01-december-2003
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Attachments to the Public Switched Telephone Network (PSTN); Basic attachment
requirements for modems standardized for use on the PSTN (Candidate NET 20)
Ta slovenski standard je istoveten z: ETS 300 114 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 300 114
TELECOMMUNICATION October 1991
STANDARD
Source: Reference:
ICS:33.040.40
ETSI TC-TE, PSTN, Modems
Key words:
Attachments to the Public Switched Telephone Network (PSTN)
Basic attachment requirements for modems standardized for use
on the PSTN
(Candidate NET 20)
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 300 114: October 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 300 114: October 1991
Contents
Foreword .7
1 Scope .9
2 Normative references.9
3 Definitions and abbreviations .10
3.1 Definitions .10
3.2 Abbreviations .11
4 Common requirements.12
4.1 General notes .12
4.2 PSTN access requirements.12
4.3 Information to be provided by the applicant.12
4.3.1 Information required for testing purposes .12
4.3.1.1 List of modes .12
4.3.1.2 Other items .12
4.3.2 Instructions for use.13
5 Requirements common to some Category II modems .13
5.1 General notes .13
5.2 Call establishment sequence based upon CCITT Recommendation V.25 [9].13
5.2.1 For modems initiating calls.13
5.2.2 For modems answering calls .14
5.3 Test loop implementation based upon CCITT Recommendation V.54 [11] .14
5.3.1 General.14
5.3.2 Remote digital test loop (loop 2).15
5.3.3 Local analogue test loop (loop 3) .15
5.4 Threshold of received line signal detection.15
5.5 Requirements for modems providing asynchronous to synchronous conversion based
upon CCITT Recommendation V.14 [8] .15
5.5.1 General.15
5.5.2 Transmission of start-stop characters.16
5.5.2.1 Signalling rate ranges of the start-stop characters at the
modem input.16
5.5.2.2 Start-stop character format.16
5.5.2.3 Asynchronous to synchronous conversion .16
5.5.2.3.1 Transmitter.17
5.5.2.3.2 Receiver.17
5.5.2.3.3 Break signal .17
5.6 Performance .18
5.6.1 Overall Performance .18
5.6.2 Performance in the presence of metering pulses .18
Annex A (Informative): Testing methods for national variants for Clause 2.20
A.1 General notes.20
Annex B (Normative): Testing methods for Clause 5 .21
B.1 General conditions for test .21
B.2 Tests of the call establishment sequence specified in subclause 5.2.21
B.2.1 For modems initiating calls .21
B.2.2 For modems answering calls.22

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ETS 300 114: October 1991
B.3 Tests to verify the test loop implementation specified in subclause 5.3. 22
B.4 Tests to verify the threshold of line signal detection. 22
B.5 Tests to verify the process of asynchronous to synchronous conversion specified in subclause
5.5. 22
B.5.1 Test patterns . 23
B.5.1.1 General . 23
B.5.1.2 Standard test text. 23
B.5.1.3 Discrete Test Characters (DTC). 23
B.5.2 Data signalling rates. 24
B.5.3.1 Transmitter tests. 25
B.5.3.1.1 Omission of stop elements . 25
B.5.3.1.2 Over-speed and under-speed capabilities . 25
B.5.3.1.3 Arbitrary character spacing . 26
B.5.3.1.4 Break signal transmission. 27
B.5.3.2 Receiver tests. 27
B.5.3.2.1 Over-speed capability . 27
B.5.3.2.2 Under-speed capability . 28
B.5.3.2.3 Character recovery. 28
B.5.3.2.4 Break signal reception . 28
B.6 Performance testing methodology. 29
B.6.1 General. 29
B.6.2 Definitions. 29
B.6.4 Method of measurement . 30
B.6.4.1 Test set-up. 31
B.6.4.2 Test 1. 32
B.6.4.3 Test 2. 35
B.6.4.4 Test 3. 36
Annex C (Normative): Description of specialised test facilities . 37
C.1 General. 37
C.2. Test set-up. 37
C.2.1 Simulated PSTN conditions . 38
C.3 Test Line 1 transmission characteristics . 43
C.3.1. Local line simulators. 43
C.3.2 Trunk network simulator. 43
C.3.3 Permanent impairments. 43
C.3.3.1 Insertion loss. 43
C.3.3.2 White noise. 43
C.3.3.3 Frequency offset and Phase roll. 51
C.3.3.4 Phase jitter. 52
C.3.3.5 Echo. 52
C.3.3.6 Harmonic distortion. 52
C.4 Test Line 2 transmission characteristics . 52
C.4.1 Local line simulators. 52
C.4.2 Trunk network simulator. 60
C.4.3 Permanent impairments. 60
C.4.3.1 Insertion loss. 60
C.4.3.2 Frequency offset and Phase roll. 60
C.4.3.3 Phase jitter. 60
C.4.3.4 Echo. 60
C.4.3.5 Harmonic distortion. 61
C.4.3.6 Noise floor. 61
C.5 Test Line 3 transmission characteristics . 61
Annex D (Normative): Provision of test tools. 62

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ETS 300 114: October 1991
Annex E (Informative): Example of proforma chart for information request.63
Annex F (Informative): Bibliography.64
History.65

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ETS 300 114: October 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
draft ETS may be utilized, wholly or in part, for the establishment of NET 20.
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 Standard (Normative references, numbers [1] to [6] inclusive).
Approval as Category I is the minimum mandatory requirement for the connection of a modem to the
Public Switched Telephone Network (PSTN), although there may be other additional requirements. Any
modem is capable of Category I approval as long as it meets the PSTN access requirements of the
country, or countries, for which approval is sought. It does not have to comply, for instance, with any of the
CCITT V. series Recommendations, nor are there any approval requirements relating to its functioning or
its performance as a modem. A modem approved as Category I may or may not be in compliance with
certain CCITT Recommendations but, since this is not tested, no assurance of interworking is implied. All
of the requirements for Category I modems are given in this ETS which in turn references draft prETS 300
001 [1].
NOTE: Clause 4 of this ETS, specifying the common requirements for modems to be attached
to the PSTN, may reference significantly differing requirements, depending upon
peculiarities of the national networks.
Approval as category II, which is applicable only when the supplier requests, is only available to modems
providing certain combinations of functionality based upon the modem specific V. series of CCITT
Recommendations. The object of Category II approval is to provide the user with the assurance that a
modem can inter-work, under most network conditions, with other compatible Category II modems.
To obtain Category II approval a modem must, in addition to meeting requirements appropriate to
Category I modems, meet the requirements given in one or more modem-specific ETS (final draft prETS
300 002 [6] and ETSs 300 115 to 300 118 ([2] 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 CCITT 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 inter-
working and do not prevent Category II approval of a modem 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 is approvable to Category II in that
mode.
It is acceptable for a modem to be tested for Category II approval 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 requirements applicable to Category I modems. The "Instructions for Use" make it clear to the user
those modes which the modem has been approved as meeting the requirements for Category II and those
which meet requirements for Category I.
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

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ETS 300 114: October 1991
for those using the modem and to ensure end-to-end interoperability between modems in compatible
configurations.
NOTE: Compliance with a modem specific ETS provides to the user the 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.
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ETS 300 114: October 1991
1 Scope
This ETS specifies the technical characteristics to be met by modems seeking approval for connection to
the PSTN. Clauses of this ETS also define the approval criteria for certain features which may be provided
by some Category II modems, but the requirements in these parts are only mandatory 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 galvanically 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 and for Clause 5 in Annex B.
Annex C describes the testing facilities which a testing laboratory may need to provide.
Annex D 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] Draft prETS 300 001 (1990): "Attachments to Public Switched Telephone
Network (PSTN); General technical requirements for equipment connected to an
analogue subscriber interface in the PSTN (T/TE 04-16) [Candidate NET 4]".
[2] ETS 300 115 (1990): "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] ETS 300 116 (1990): "Attachments to the Public Switched Telephone Network
(PSTN); Category II attachment requirements for 1200 bits per second duplex
modems standardized for use on the PSTN [Candidate NET 22]".
[4] ETS 300 117 (1990): "Attachments to the Public Switched Telephone Network
(PSTN); Category II attachment requirements for 2400 bits per second duplex
modems standardized for use on the PSTN [Candidate NET 23]".
[5] ETS 300 118 (1990): "Attachments to the Public Switched Telephone Network
(PSTN); Category II requirements for 1200 bits per second half-duplex and
1200/75 bits per second asymmetrical duplex modems standardized for use on
the PSTN [Candidate NET 24]".
[6] Final draft prETS 300 002 (1991): "Public Switched Telephone Network (PSTN);
Approval requirements for 9600 or 4800 bits per second duplex modems
standardized for use on the PSTN (T/TE 04-09) [Candidate NET 25].
[7] CCITT Recommendation V.24 (1984): "List of definitions for interchange circuits
between Data Terminal Equipment and Data Circuit-Terminating Equipment".
[8] CCITT Recommendation V.14 (1988): "Transmission of start-stop characters
over synchronous bearer channels".

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ETS 300 114: October 1991
[9] 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".
[10] CCITT Recommendation V.21 (1984): "300 bits per second duplex modem
standardized for use in the General Switched Telephone Network".
[11] CCITT Recommendation V.54 (1984): "Loop test devices for modems".
[12] CCITT Recommendation V.4 (1984): "General structure of signals of
international Alphabet No. 5 Code for data transmission over Public Telephone
Networks".
[13] 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".
[14] CCITT Recommendation V.52 (1984): "Characteristics of distortion and error-
rate measuring apparatus for data transmission".
[15] 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".
[16] 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".
[17] CCITT Recommendation V.23 (1984): "600/1200- Baud modem standardized
for use in the General Switched Telephone Network".
[18] 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.
3 Definitions and abbreviations
3.1 Definitions
For the purpose of this and other related ETSs, the following definitions apply:
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 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.
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 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, a bilateral agreement on
the use of call mode and answer mode shall be necessary.

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ETS 300 114: October 1991
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.
Intracharacter signalling rate: the intracharacter 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 shall be designed:
- to meet the requirements of the same CCITT Recommendation(s) as the modem under test,
to the extent necessary for performing the tests;
- to provide the functionalities for a modem used for reference that are specified in the relevant
testing Clauses, and
- to provide an interface which is accessible and of a type suitable for use in the tests (e.g.
CCITT Recommendation V.24 [7]).
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.
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 [7] 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.
Silence: signals which in the relevant frequency band have an in-band power level which is at least 30 dB
below the level of the transmitted signal at the point of measurement. This term is used to describe
periods where signals are not transmitted during the hand-shaking sequences.
3.2 Abbreviations
AMM Answer Mode Modem
CCITT Comité Consultatif International Télégraphique et Téléphonique
CcT Circuit
CEPT Conférence Européenne des Administrations des Postes et des
Télécommunications
CMM Call Mode Modem
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ETS 300 114: October 1991
DCE Data Circuit-Terminating Equipment
DTE Data Terminal Equipment
ETS European Telecommunications Standard
ETSI European Telecommunications Standards Institute
MCT Modem Conformance Tester
PSTN Public Switched Telephone Network
4 Common requirements
4.1 General notes
This Clause specifies the requirements to be met by all modems seeking Category I or Category II
approval for use on the PSTN.
4.2 PSTN access requirements
The requirements of Draft prETS 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);
- approval domain (Category I and/or Category II);
- countries for which approval is sought.
An example of proforma chart to collect these 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 approval is sought:
- list of carrier modes;
- automatic answering;
- automatic calling;
- provision of line loop 3 during a connection;
- special features.
NOTE: Operation in modes not approved for use on a specific PSTN is prohibited in the
country concerned.
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: October 1991
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 Category I approval has been given;
c) any information specifically indicated in this ETS for inclusion in the "Instructions for use"; and
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];
- ETS 300 116 [3];
- ETS 300 117 [4];
- ETS 300 118 [5];
- final draft prETS 300 002 [6].
On the whole, these requirements are based upon, and do not conflict with, CCITT Recommendations,
nevertheless some exceptions have been introduced in subclause 5.5 (for asynchronous to synchronous
conversion based upon CCITT Recommendation V.14 [8]) 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 [7]. 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 [7] 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 [9]
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.
The provision of a calling tone as described in CCITT Recommendation V.25 [9] is optional. Where this
facility has been provided the calling tone shall be 1300 Hz with the exception of CCITT Recommendation
V.21 [10] modems where it shall be either 980 Hz or 1300 Hz. Multi-mode modems providing this facility
shall use 1300 Hz.
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 2078 Hz to 2122 Hz indicating
that the remote modem has connected to line, the modem shall not give an indication to the DTE that it is

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ETS 300 114: October 1991
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: 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: These requirements are derived from the Clauses 3.18 to 3.20 of CCITT
Recommendation V.25 [9]; the calling tone and calling station response, if present,
should only be constrained by Draft prETS 300 001 [1].
Compliance shall be checked by the method described in Annex B.2.1
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 and not more than 2,5 s. The modem, or its associated automatic answering equipment, shall then
transmit 2100 Hz ± 15 Hz for a period of 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 [9].
NOTE 2: The level at which the tone is transmitted is constrained by Draft prETS 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
2100 Hz tone at 450 ms ± 25 ms intervals.
Compliance shall be checked by the method described in Annex B.2.2.
5.3 Test loop implementation based upon CCITT Recommendation V.54 [11]
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.
Figure 1 roughly indicates the function of these test loops.

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ETS 300 114: October 1991
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.
5.5 Requirements for modems providing asynchronous to synchronous conversion based
upon CCITT Recommendation V.14 [8]
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:

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ETS 300 114: October 1991
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 [8]. If an
error correction function is to be included in the modem, asynchronous to synchronous
conversion as described in Recommendation V.42 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.
NOTE 1: It is assumed that characters presented to the modem are in accordance with CCITT
Recommendation V.4 [12]. 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 intracharacter signalling rate of the start-stop
characters and the data signalling rate of the synchronous bearer channel shall be by insertion or deletion
of stop elements at the transmitter and re-insertion of deleted stop elements at the receiver. The means
shall also be provided for transfer of continuous start polarity (break signals).

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ETS 300 114: October 1991
5.5.2.3.1 Transmitter
In the transmit direction the start-stop characters shall be adapted to the signalling rate of the
synchronous bearer channel by:
- transmission of start and data elements in the same sequence as in the start-stop
characters;
- insertion of additional stop elements in the case of under-speed of the start-stop characters;
- deletion of stop elements in the case of over-speed of the start-stop characters.
When the modem is set to operate in the basic signalling rate range, the number of stop elements deleted
less the number of additional stop elements inserted (if any), measured over any eight consecutively
transmitted characters, shall not be greater than one, and when, the modem is set to operate in the
extended signalling rate range, the number of stop elements deleted less the number of additional stop
elements inserted (if any), measured over any four consecutively transmitted characters, shall not be
greater than one.
Compliance shall be checked by the method described in Annex B, subclauses B.5.3.1.1, B.5.3.1.2, and
B.5.3.1.3.
5.5.2.3.2 Receiver
In order to recover a start-stop character structure, the receiver part of the conversion process shall
regenerate the start and data elements transmitted on the synchronous bearer and restore the stop
elements which have been deleted by the transmitter part of the conversion process.
The intracharacter signalling rate provided by the receiving modem (to the DTE) shall be not less than the
lower limit of the nominal synchronous line signalling rate and not more than the limit of the specified over-
speed tolerance, viz +1% for the basic signalling rate range and +2,3% for the extended signalling rate
range. The length of stop elements output to the receiving DTE shall not be reduced by more than 15,7%
in the basic signalling rate range (or 28,2% in the extended signalling rate range), relative to the nominal
synchronous line signalling rate.
For any character, the length of the start element and the lengths of each data element shall differ by no
more than 6,5% from the nominal element length, "NEL", for that character as defined by the equation:
sum of lengths of start element and data elements
NEL = -------------------------------------------------------------------
number of data elements + 1
Compliance shall be checked by the method described in Annex B, subclauses B.5.3.2.1, B.5.3.2.2 and
B.5.3.2.3.
5.5.2.3.3 Break signal
5.5.2.3.3.1 Transmitter
When the digital interface of the modem is presented with asynchronous data signals comprising between
M and 2M + 3 bits of "start" polarity, where M is the number of bits per character in the selected format,
the modem shall transmit 2M + 3 bits of "start" polarity. If the modem is presented with more than 2M + 3
bits all of "start" po
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