ETSI ETS 300 118 ed.1 (1991-06)

Attachments to the Public Switched Telephone Network (PSTN); Category II attachment 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)

T/TE 04-21 [AI]

Priključitve na javno komutirano telefonsko omrežje (PSTN) – Priključitvene zahteve kategorije II za poldupleksne modeme za hitrosti 1200 b/s in asimetrične dupleksne modeme za hitrosti 1200/75 b/s, standardizirane za uporabo v PSTN

General Information

• Status: Published
• Publication Date: 22-Sep-1991
• Technical Committee: TE 5 - General Terminal Access Requirements
• Current Stage: 12 - Completion
• Due Date: 13-Jul-1990
• Completion Date: 23-Sep-1991
• Ref Project: SIST ETS 300 118 E1:2003 - Attachments to the Public Switched Telephone Network (PSTN); Category II attachment 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)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 118 E1:2003
01-december-2003
3ULNOMXþLWYHQDMDYQRNRPXWLUDQRWHOHIRQVNRRPUHåMH3671±3ULNOMXþLWYHQH
]DKWHYHNDWHJRULMH,,]DSROGXSOHNVQHPRGHPH]DKLWURVWLEVLQDVLPHWULþQH
GXSOHNVQHPRGHPH]DKLWURVWLEVVWDQGDUGL]LUDQH]DXSRUDERY3671
Attachments to the Public Switched Telephone Network (PSTN); Category II attachment
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)
Ta slovenski standard je istoveten z: ETS 300 118 Edition 1
ICS:
33.040.35 Telefonska omrežja Telephone networks
SIST ETS 300 118 E1:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 118 E1:2003

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SIST ETS 300 118 E1:2003
EUROPEAN ETS 300 118
TELECOMMUNICATION June 1991
STANDARD
Source: ETSI TC-TE Reference: T/TE 04-21
ICS: 33.020, 33.040.40
PSTN, modems
Key words:
Attachments to the Public Switched Telephone Network (PSTN)
Category II attachment requirements for 1200 bits per second
half duplex and 1200/75 bits per second asymmetrical 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 24)
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 - [e-mail]
X.400: Internet:
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 1991. All rights reserved.
New presentation - see History box

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ETS 300 118: 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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Contents
Foreword.5
1 Scope .7
2 Normative references .7
3 Definitions and abbreviations.7
3.1 Definitions.7
3.2 Abbreviations.8
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 .9
5.1 General requirements.9
5.2 Modes of operation/use. 10
5.3 Line signals. 10
5.3.1 Carrier frequencies. 10
5.3.2 Spectral power . 10
5.4 Line signalling rates. 11
5.5 Channel allocation . 11
5.6 Response times. 11
5.6.1 Response times of the forward channel and backward channel received
line signal detectors. 11
5.6.2 Response times of the forward channel ready for sending indicator. 12
5.6.2.1 For modems with DTE control . 12
5.6.2.2 For modems with control derived from the backward
channel . 12
5.6.2.3 For modems which transmit carrier constantly when in the
on-line state . 13
5.6.3 Response times of the backward channel ready for sending indicator. 13
5.6.3.1 For modems with DTE control . 13
5.6.3.2 For modems with control derived from the forward
channel . 13
5.7 Synchronous mode of use. 14
5.8 Thresholds of received line signal detectors . 14
5.9 Auto-calling and auto-answering procedures. 14
5.9.1 Auto-calling - calling tone . 14
5.9.2 Auto-calling- recognition of answering tone. 14
5.9.3 Auto-answering - answer tone. 14
5.10 Provision of test looping facilities. 15
5.11 Performance. 15
5.11.1 Distortion. 15
5.11.2 Receiver performance . 15
Annex A (Normative): Testing methods . 16
A.1 General testing conditions. 16
A.2 Test for subclause 5.3.1 (Carrier frequencies). 16

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A.3 Test for subclause 5.5 (Channel allocation).16
A.4 Test for subclause 5.6 (Response times) .16
A.4.1 Test for subclause 5.6.1 .17
A.4.2 Test for subclause 5.6.2 (Data channel Ready For Sending (RFS) response times).17
A.4.2.1 Test for subclause 5.6.2.1.17
A.4.2.2 Test for subclause 5.6.2.2.17
A.4.2.3 Test for subclause 5.6.2.3.17
A.4.3 Test for subclause 5.6.3 (Backward channel RFS response times) .18
A.4.3.1 Test for subclause 5.6.3.1.18
A.4.3.2 Test for subclause 5.6.3.2.18
A.5 Test for subclause 5.7 (Synchronous mode of use).18
A.6 Test for subclause 5.11.1 (Distortion) .18
A.6.1 Test for subclause 5.11.1 (a) .19
A.6.2 Test for subclause 5.11.1 (b) .19
A.6.3 Test for subclause 5.11.1 (c) .19
Annex B (Informative): Proforma declaration of modes of operation/use.20
History .22

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ETS 300 118: June 1991
Foreword
This European Telecommunication Standard (ETS) was produced by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI) and adopted in
November 1990. The text of this draft ETS may be utilized, wholly or in part, for the establishment of NET
24.
This ETS contains the technical requirements for approval to Category II of 1200 bits per second half
duplex and 1200/75 bits per second asymmetrical duplex modems standardized for use on the Public
Switched Telephone Network (PSTN). Approval and testing to Category II is applicable only at the request
of the applicant. These requirements are based upon, and do not conflict with, CCITT Recommendation
V.23 [4] except in the case of subclause 5.3.1 where the frequency tolerances specified are tighter than
those given.
Additionally, requirements are included relating to end-to-end inter-operability over PSTN connections.
Such requirements are in excess of the CCITT Recommendations. A modem which complies with CCITT
Recommendation V.23 [4] should always meet the requirements of this ETS which relate to parameters
specified in that CCITT Recommendation.
Clause 4 of this ETS references the requirements common to both Category I and II modems, which are
contained in ETS 300 114 [2], Clause 4.
Clause 5 of this ETS contains Category II requirements specific to 1200 bits per second half duplex and
1200/75 asymmetrical 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.

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1 Scope
This European Telecommunication Standard (ETS) specifies the technical characteristics to be met by a
modem seeking Category II approval for
- half duplex operation over the PSTN at 1200 bits per second; and/or
- asymmetrical duplex operation over the PSTN at 1200/75 bits per second.
The modulation schemes specified are those described in CCITT Recommendation V.23 [4].
The term "modem" in the context of this ETS includes all physical implementation practices for a voice
band modem, which are galvanically connected to the PSTN.
This ETS specifies four modes of operation/use (see subclause 5.2).
This ETS also contains descriptions of the tests to be performed in order to confirm compliance with the
functional requirements contained herein. A general description of the test conditions and test requirements
is given in Annex A (Normative).
NOTE: To aid reading, the term "forward channel" is sometimes used to describe the channel
capable of transmitting up to 1200 bit/s, and the term "backward channel" is similarly
used to describe the channel capable of transmitting up to 75 bit/s.
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 (candidate NET4)"
[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.23 (1984), "600/1200-Baud modem standardized for
use in the General Switched Telephone Network"
3 Definitions and abbreviations
For the purposes of this standard the definitions and abbreviations contained in ETS 300 114 [2] shall
apply, together with the following.
3.1 Definitions
Data Terminal Equipment (DTE): 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 other suitable device may
monitor or generate such signals.

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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 start-stop 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.
Modem: a functional unit that modulates and demodulates 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;
- 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).
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: in the context of this ETS, modes of operation are defined as modes specified in this
modem-specific ETS that have an influence upon line signals present at the PSTN interface.
Modes of use: in the context of this ETS, modes of use are defined as modes specified in this modem-
specific ETS that have an influence upon conditions present at a digital interface. Examples include a
"conventional" CCITT Recommendation V.24 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
CCITT Comité Consultatif International Télégraphique et Téléphonique
Cct Circuit
CEPT Conférence Européenne des Administrations des Postes et des
Télécommunications
DCE Data Circuit-Terminating Equipment
DTE Data Terminal Equipment

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ETS 300 118: June 1991
ISO Organization for International Standardization (French Terminology)
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 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 for which of the modes of operation/use identified in this ETS approval to
Category II is sought.
Compliance will be considered to have been accomplished by provision of the relevant information.
NOTE : This may be carried out by completion of forms such as those 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.
For the purpose of compliance with this standard, any additional information 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
- half-duplex mode with switched carrier or asymmetrical duplex mode of operation/use with
continuous carriers, as specified in CCITT Recommendation V.23 [4],
- frequency shift binary modulation with synchronous or asynchronous mode of use,
- signalling rates of up to 1200 bit/s in the forward channel and, optionally, of up to 75 bit/s in the
backward channel.
NOTE 1: In the following, references are made to interchange circuits between the modem and
the DTE, as defined in CCITT Recommendation V.24. DTEs using certain customised
modems will generally not provide an interface with such interchange circuits. For these
cases the references to V.24 type interchange circuits indicate equivalent functionality
of a DTE and a modem.

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NOTE 2: With asymmetrical duplex modems providing a CCITT Recommendation V.24 interface,
it is common practice to provide the interchange circuit for the 75 bit/s channel on the
relevant pin for the 1200 bit/s channel.
5.2 Modes of operation/use
It shall be possible to configure the modem to operate in at least one of the following modes of
operation/use:
a) 1200/1200 bit/s half duplex asynchronous
b) 1200/75 bit/s asymmetrical duplex asynchronous
c) 75/1200 bit/s asymmetrical duplex asynchronous
d) 1200/1200 bit/s half duplex synchronous
It is the applicant's responsibility to specify for which of these modes of operation/use approval for
Category II is sought.
NOTE 1: In the above representation, the first number indicates the rate at which data is
received, and the second number indicates the rate at which data is transmitted.
NOTE 2: In this ETS, it is not possible to make a clear distinction between mode of operation
and mode of use, and therefore no attempt has been made to separate the above list
into these categories.
5.3 Line signals
The channels defined are within the telephone bandwidth.
NOTE: The allocation of channels is described in subclause 5.5.
5.3.1 Carrier frequencies
The nominal characteristic frequencies are listed in Table 1:
Table 1: Frequency allocation
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡         ‡  Binary 0 (Fa)   ‡   Binary 1 (Fz)  ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡ 1200 bit/s chl. ‡   2100 Hz     ‡    1300 Hz   ‡
ˆ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡75 bit/s channel ‡   450 Hz     ‡     390 Hz   ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
For modes a), c) and d), as defined in subclause 5.2, the characteristic frequencies Fa and Fz as
measured at the line terminals of the modem shall not deviate by more than ± 3 Hz for the 1200 bit/s
channel; and for mode b) ± 2 Hz for the 75 bit/s channel (if provided in the modem) from those given in
Table 1.
NOTE : These frequency tolerance are tighter than those specified by CCITT Recommendation
V.23 [4].
Compliance shall be checked by the method described in Annex A, Clause A.2
5.3.2 Spectral power
The national network dependent spectral power limits are given in ETS 300 114 [2], Clause 4.
NOTE : This refers in turn to Draft prETS 300 001 [1].

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5.4 Line signalling rates
Where the modem provides the relevant mode(s) of operation, it shall be capable of transmitting and/or
receiving data at line signalling rates of:
- up to 1200 bit/s in modes (a), (b) and (c);
- up to 75 bit/s in modes (b) and (c); and
- 1200 bit/s in mode (d).
Compliance shall be checked during the tests given in subclause 5.11.
5.5 Channel allocation
For modems capable of alternating between modes b) and c) (asymmetrical duplex modems) whilst in the
on-line state, two methods of controlling transmission in the 75 bit/s channel are recognized for
asymmetrical duplex modems, either:
a) the modem shall enable transmission on the 1200 bit/s channel when the DTE indicates that it
wishes to transmit on the 1200 bit/s channel (equivalent: turning ON Cct 105); and the modem shall
enable transmission on the 75 bit/s channel when the DTE indicates that it no longer wishes to
transmit on the 1200 bit/s channel (equivalent: turning OFF Cct 105);
Compliance shall be checked by the method described in Annex A, Clause A.3.
or,
b) the control of transmission on the 75 bit/s channel shall be on a separate circuit (equivalent: Cct
120) to that for the 1200 bit/s channel, in which case the response times of the ready for sending
indicators shall comply with subclauses 5.6.2.2 and 5.6.3.2.
Compliance is checked during performance of the test associated with subclauses 5.6.2.2 and 5.6.3.2.
5.6 Response times
5.6.1 Response times of the forward channel and backward channel received line signal
detectors
The response times of the 1200 bit/s channel and the 75 bit/s channel received line signal detectors are
the times that elapse between :
a) For the OFF to ON transition: the application of a tone corresponding to binary 1 at a level higher
than -43 dBm to the line terminals of the modem and an indication being given to the DTE that a
carrier signal has been detected (equivalent: turning ON Cct 109).
b) For the ON to OFF transition: removal of a tone corresponding to binary 1 from, or the level falling
instantaneously to below -48 dBm, at the line terminals of the modem and an indication being given
to the DTE that a carrier signal is no longer being detected (equivalent: turning OFF Cct 109).
The response times of the detector shall be within the limits stated in Table 2.
Compliance shall be checked by the method described in Annex A subclause A.4.1.

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Table 2: Received line signal detector response times
�˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜´˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜¿
‡ Data  ‡ OFF to ON ‡ 300 ms to 2000 ms  10 ms to 20 ms ‡
‡ Channel ‡      ‡     (see Note 1 below)     ‡
‡ Signal ˆ˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡ Detector‡ ON TO OFF ‡      5 ms to 15 ms      ‡
ˆ˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡ Backward ‡ OFF to ON ‡       < 80 ms        ‡
‡ Chl.   ‡      ‡                   ‡
‡ Signal  ˆ˜˜˜˜˜˜˜˜˜˜˜˜¯˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡ Detector ‡ ON TO OFF ‡     15 ms to 120 ms      ‡
‡     ‡      ‡    (see Note 2 below)      ‡
ˆ˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜`˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜·
‡NOTE 1: The longer range of response times is only to be used‡
‡    during call establishment in association with    ‡
‡    automatic calling and answering.           ‡
‡                               ‡
‡NOTE 2: CCITT Recommendation V.23 [4] suggests a value of 15 ‡
‡    ms to 80 ms.                     ‡
�˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜�
5.6.2 Response times of the forward channel ready for sending indicator
The applicant shall state whether the ready for sending delay is either a) or b) or both of Table 3, and that
information shall be included in the instruction for use.
The response times of the 1200 bit/s channel ready for sending indicator are those given in subclauses
5.6.2.1 to 5.6.2.3.
5.6.2.1 For modems with DTE control
The response times of the 1200 bit/s channel ready for sending indicator are the times that elapse
between:
a) for the OFF to ON transition: a DTE indicating that it wishes to transmit in the 1200 bit/s channel
(equivalent: turning ON Cct 105) and an indication being given to the DTE that the 1200 bit/s channel
is ready (equivalent: turning ON Cct 106), for modes a), c) and d);
b) for the ON to OFF transition: a DTE indicating that it no longer wishes to transmit in the 1200 bit/s
channel (equivalent: turning OFF Cct 105) and an indication being given to the DTE that the 1200
bit/s channel is no longer ready (equivalent: turning OFF Cct 106), for modes a), c) and d).
Compliance shall be checked by the method described in Annex A subclause A.4.2.1
5.6.2.2 For modems with control derived from the backward channel
For a modem in which control of the transmitted carrier in the 1200 bit/s channel is controlled by the
reception of signals from the remote modem in the 75 bit/s channel, the response times of the 1200 bit/s
channel ready for sending indicator are the times that elapse between:
a) for the OFF to ON transition: an indication to the DTE that a carrier signal has been received in the
75 bit/s channel (equivalent: turning ON Cct 122) and an indication being given to the DTE that the
1200 bit/s channel is ready (equivalent: turning ON Cct 106);
b) for the ON to OFF transition; an indication to the DTE that a carrier signal is no longer being
received in the 75 bit/s channel (equivalent: turning OFF Cct 122) and an indication being given to
the DTE that the 1200 bit/s channel is no longer ready (equivalent: turning OFF Cct 106).
Compliance shall be checked by the method described in Annex A subclause A.4.2.2

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5.6.2.3 For modems which transmit carrier constantly when in the on-line state
The response times of the 1200 bit/s channel ready for sending indicator are the times that elapse
between:
a) for the OFF to ON transition; an indication being given to the DTE that the modem is ready to
operate (equivalent: turning ON Cct 107) and an indication being given to the DTE that it is able to
transmit on the 1200 bit/s channel (equivalent: turning ON Cct 106);
b) for the ON to OFF transition; an indication being given to the DTE that the modem is no longer ready
to operate (equivalent: turning OFF Cct 107) and an indication being given to the DTE that the 1200
bit/s channel is no longer ready (equivalent: turning OFF Cct 106).
The response times of the detector shall be within the limits stated i
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