IEC 61811-50:2002

IEC 61811-50 ®
Edition 2.0 2002-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electromechanical all-or-nothing relays –
Part 50: Sectional specification – Electromechanical all-or-nothing telecom
relays of assessed quality
Relais électromécaniques de tout-ou-rien –
Partie 50: Spécification intermédiaire – Relais électromécaniques de tout-ou-rien
télécom sous assurance de la qualité

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing more than 30 000 terms and
Technical Specifications, Technical Reports and other definitions in English and French, with equivalent terms in 14
documents. Available for PC, Mac OS, Android Tablets and additional languages. Also known as the International
iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a More than 55 000 electrotechnical terminology entries in
variety of criteria (reference number, text, technical English and French extracted from the Terms and Definitions
committee,…). It also gives information on projects, replaced clause of IEC publications issued since 2002. Some entries
and withdrawn publications. have been collected from earlier publications of IEC TC 37,

77, 86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient plus de 30 000 termes et définitions en
Spécifications techniques, Rapports techniques et autres
anglais et en français, ainsi que les termes équivalents dans
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
14 langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
Plus de 55 000 entrées terminologiques électrotechniques, en
La recherche avancée permet de trouver des publications IEC
en utilisant différents critères (numéro de référence, texte, anglais et en français, extraites des articles Termes et
comité d’études,…). Elle donne aussi des informations sur les Définitions des publications IEC parues depuis 2002. Plus
projets et les publications remplacées ou retirées. certaines entrées antérieures extraites des publications des

CE 37, 77, 86 et CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
csc@iec.ch.
IEC 61811-50 ®
Edition 2.0 2002-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electromechanical all-or-nothing relays –

Part 50: Sectional specification – Electromechanical all-or-nothing telecom

relays of assessed quality
Relais électromécaniques de tout-ou-rien –

Partie 50: Spécification intermédiaire – Relais électromécaniques de tout-ou-

rien télécom sous assurance de la qualité

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 29.120.70 ISBN 978-2-8322-1547-0

– 2 – IEC 61811-50:2002 © IEC 2002
CONTENTS
FOREWORD . 3

1 General . 5
1.1 Scope . 5
1.2 Normative references . 5
1.3 Terms and definitions . 6
1.4 Preferred values . 7
1.5 Marking and documentation . 8
2 Quality assessment procedures . 9
2.1 Primary stage of manufacture . 9
2.2 Structurally similar relays . 9
2.3 Subcontracting . 9
2.4 Qualification approval procedures . 9
2.5 Quality conformance inspection . 9
2.6 Test schedule . 10
2.7 Order of tests . 10
3 Preparation of blank detail and detail specifications . 11
4 Test schedule . 12
4.1 Test sequence . 12
4.2 Types of relays, based upon environmental protection (relay technology RT) . 12
4.3 Categories of application of contacts . 12
4.4 Notes relative to Table 1 . 13
5 Relay reliability - Failure rate data . 13

Annex A (informative) Data base for failure rates . 18

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMECHANICAL ALL-OR-NOTHING RELAYS –

Part 50: Sectional specification –
Electromechanical all-or-nothing telecom relays
of assessed quality
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61811-50 has been prepared by IEC technical committee 94:
All-or-nothing electrical relays.
This bilingual version (2014-04) corresponds to the English version, published in 2002-03.
This second edition of IEC 61811-50 cancels and replaces the first edition published in 1997
and constitutes a technical revision.

– 4 – IEC 61811-50:2002 © IEC 2002
The text of this standard is based on the following documents:
FDIS Report on voting
94/144/FDIS 94/158/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
The committee has decided that the contents of this publication will remain unchanged until
2007. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
ELECTROMECHANICAL ALL-OR-NOTHING RELAYS –

Part 50: Sectional specification –
Electromechanical all-or-nothing telecom relays
of assessed quality
1 General
1.1 Scope
This part of IEC 61811 is a sectional specification and applies to electromechanical all-or-
nothing telecom relays of assessed quality. Relays according to this standard are provided for
operation in telecommunication applications. However, as electromechanical all-or-nothing
relays, they are also suitable for particular industrial and other applications.
This standard selects from IEC 61810-7 and other sources the appropriate methods of test to
be used in detail specifications derived from this specification, and contains basic test
schedules to be used in the preparation of such specifications. Detailed test schedules are
contained in the blank detail specifications supplementary to this specification.
1.2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60062:1992, Marking codes for resistors and capacitors
IEC 60255-23:1994, Electrical relays – Part 23: Contact performance
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60695-2-2:1991, Fire hazard testing – Part 2: Test methods – Section 2: Needle-flame test
IEC 61709:1996, Electronic components – Reliability – Reference conditions for failure rates
and stress models for conversion
IEC 61810-1:1998, Electromechanical non-specified time all-or-nothing relays – Part 1:
General requirements
IEC 61810-5:1998, Electromechanical non-specified time all-or-nothing relays – Part 5:
Insulation co-ordination
– 6 – IEC 61811-50:2002 © IEC 2002
IEC 61810-7:1997, Electromechanical all-or-nothing relays – Part 7: Test and measurement
procedures
IEC 61811-1:1999, Electromechanical non-specified time all-or-nothing relays of assessed
quality – Part 1: Generic specification
QC 001002-3:1998, Rules of Procedure of the IEC Quality Assessment System for Electronic
Components (IECQ) – Part 3: Approval Procedures
ISO 8601:2000, Data elements and interchange formats – Information interchange –
Representation of dates and times
ISO 9001:2000, Quality systems – Model for quality assurance in design, development,
production, installation and servicing
CECC 00016:1990, Basic requirements for the use of statistical process control (SPC) in the
CECC system
CECC 00800:1986, Code of practice on the use of the ppm approach in association with
the CECC system
1.3 Terms and definitions
For the purpose of this part of IEC 61811, the terms and definitions given in IEC 61810-7, as
well as the following apply:
1.3.1
types of relays
types of relays as defined in IEC 61810-7
NOTE The most frequent types of electromechanical all-or-nothing telecom relays are the following ones:
– monostable: non-polarized;
– monostable: polarized;
– bistable: polarized.
1.3.2
types of contacts
a) change-over break-before-make contact
change-over contact, one contact circuit of which breaks before the other makes
b) change-over make-before-break contact
change-over contact, one contact circuit of which makes before the other breaks
1.3.3
contact fault and contact failure
a) contact fault due to contact-circuit resistance
the occurrence is assumed when the contact-circuit resistance of a closed contact exceeds
the maximum value stated in the detail specification
b) contact fault due to non-opening of the contact circuit (e.g. contact sticking)
the occurrence due to the fact that the contact does not open is assumed when the resistance
of an open contact assembly falls below the specified minimum value stated in the detail
specification
c) contact failure
the occurrence is assumed when the number of faults due to contact-circuit resistance or/and
of faults due to non-opening of the contact circuit exceeds the number of faults stated in the
detail specification, with reference to a single tested contact
1.3.4
relay fault, relay failure and relay defect
a) relay fault
the state of a relay characterized by the inability to perform a required function. A fault
persists for a limited time after which the relay recovers the ability to perform a required
function without being subjected to any corrective maintenance
b) relay failure
failure occurs when the relay is unable to carry out its required function
c) relay defect
any deviation of a characteristic of a relay from the requirements
NOTE 1 The requirements may or may not be expressed in the form of a specification.
NOTE 2 A defect may or may not affect the ability of a relay to perform a required function.
d) defective relay
relay containing one or more defects
1.4 Preferred values
The following Subclauses contain preferred values applicable to electromechanical all-or-
nothing telecom relays.
1.4.1 Rated coil voltages
Preferred values d.c.: 1,5; 3; 4,5; 5; 6; 9; 12; 24; 48 or 60 V.
1.4.2 Contact-circuit resistance
a) Preferred values in initial condition: maximum 50; 100 or 200 mΩ.
b) Preferred values during/after tests: maximum 0,5; 1; 5; 10; 20 or 100 Ω.
c) Preferred value for detecting faults due to non-opening of the contact circuit during tests:
minimum 100 kΩ.
d) Voltage for detecting faults due to non-opening of the contact circuit during tests;
preferred maximum values: 0,03; 5; 6; 12; 24; 48 or 60 V d.c.
e) Difference of contact-circuit resistance between different contact circuits in the same
relay, preferred value: maximum 100 mΩ (initial condition).
1.4.3 Dielectric test
Preferred values in initial condition between opened contact circuits, between separate
contact circuits, between contact circuits and coil(s), between all conductive parts and mass
(if applicable) in accordance with IEC 61810-5.
a) Preferred voltages: 0,5; 0,8; 1,5; 2,5 kV a.c.
b) Preferred duration: 1 s or 60 s

– 8 – IEC 61811-50:2002 © IEC 2002
1.4.4 Impulse voltage test
a) Preferred voltages: 0,5; 1,0; 1,5; 2 or 2,5 kV.
b) Preferred waveform: 0,5 µs/700 µs, 1,2 µs/50 µs or 10 µs/700 µs.
c) Preferred number of pulses (alternate positive and negative pulses): 10.
d) Preferred frequency of pulses: 2 or 4 pulses/min.
1.4.5 Insulation resistance
Preferred value: 1 000 MΩ at 500 V d.c. initial value.
1.4.6 Number of operations determining electrical endurance
Preferred values: 10 000; 20 000; 50 000; 100 000; 200 000; 500 000; 700 000; 1 000 000;
1 600 000; 2 000 000; 5 000 000; 10 000 000; 20 000 000 or 30 000 000.
1.4.7 Contact failure rate for test evaluation purposes
–5 –6 –7 –8
Preferred values: maximum 10 , 10 , 10 , 10 /contact/cycle.
1.5 Marking and documentation
Relays and their package supplied in accordance with detail specifications covered by this
sectional specification shall be marked as follows:
1.5.1 Marking of the relay
a) Manufacturer's name, logo or trade mark.
b) Relay type and variant code.
c) Coded date of manufacture, in terms of year/week according to 1.5.3.
d) IECQ in letters or IECQ mark of conformity.
e) Identification of terminal No. 1.
1.5.2 Marking of the package
a) Manufacturer's name, logo or trade mark.
b) Relay type and variant code.
c) Manufacturer's batch identification code.
d) IECQ in letters or IECQ mark of conformity.
e) Detail specification reference if not marked on the relay.
f) Quantity.
1.5.3 Coded date of manufacture
The marking system shall use four figures as specified in 5.2 of IEC 60062. The first two
figures shall be the last two figures of the year and the last two figures the numbering of the
week (5.2.3.3 b) of ISO 8601, year and week in the current century, modified).
Example: Fifth week of 1994 = 9405.

If stated in the detail specification only, the basic format for a specific date in accordance with
5.2.1.3 a) of ISO 8601 shall be used. The first two figures shall be the last two figures of the
year, the month is represented by the next two figures and the day of the month is
represented by the last two figures.
Example: 20th June 1994 = 940620.
2 Quality assessment procedures
2.1 Primary stage of manufacture
The primary stage of manufacture is the first process subsequent to the manufacture of
finished parts and subassemblies of the relay.
NOTE 1 A subassembly is understood to mean here the permanent assembly of two or more piece parts.
NOTE 2 Important manufacturing steps are as follows:
a) fabrication, heat treatment and plating of the component parts of the relay;
b) coil winding;
c) assembling of the electrical and electromechanical parts;
d) adjustment of the relay contacts, if applicable;
e) high-temperature drying, gas backfilling and sealing of the relay, if applicable;
f) final measurements and periodic inspection of test groups A to C.
2.2 Structurally similar relays
Relays are considered structurally similar if they have no differences in design other than:
a) coil wire diameter and number of windings;
b) types, numbers and material of contacts;
c) rated coil and/or contact voltage(s);
d) mounting and terminal variants within the limits prescribed in the detail specification;
e) biasing of the input circuit parts.
2.3 Subcontracting
For subcontracting, see annex B to Clause 2 of QC 001002-3.
2.4 Qualification approval procedures
Qualification approval tests shall include all the tests prescribed in the detail specification and
shall be performed by a schedule specifically prescribed in the detail specification.
The number of specimens for each subgroup is specified in the blank detail specification. As a
general rule, a minimum of five specimens are required for each group of tests.
2.5 Quality conformance inspection
2.5.1 Formation of inspection lots
Inspection lots submitted to groups A and B acceptance tests shall be formed in accordance
with 3.2.3 of QC 001002-3 and with the sampling plans and procedures given in IEC 60410,

– 10 – IEC 61811-50:2002 © IEC 2002
except where production is too infrequent or too small for sampling plans to apply; in these
cases inspection shall be 100 %.
When sampling is carried out in accordance with IEC 60410, the percent defective concept
only shall be used. Stratified or representative sampling shall always be used to include all
production lines and structurally similar relays in proportion to their respective quantities in
the lot. Exceptions from proportionality may become necessary and shall be stated in the
detail specification. Specimens shall be as representative as possible of the production.
The determination basis for the sample sizes from continuous production lines shall be stated
in the blank detail specification.
2.5.2 Periodic inspection
Fixed sample sizes for group C inspection shall be taken from a lot (or lots) which has (have)
passed groups A and B inspection during or at the end of the specified reference period.
2.6 Test schedule
2.6.1 Test sequence
A test sequence shall consist of all tests listed in the detail specification. Where appropriate,
the reference number of the tests are those of the IEC 61810-7. Additional testing may be
called for by the detail specification.
2.6.2 Groups A and B
The inspection level (IL) notation applies to all tests in one subgroup. A corresponding
value/range of values of the acceptable quality level (AQL) shall be given in the blank detail
specification, and the authority preparing detail specifications shall choose the appropriate
value, which then applies to all tests in one subgroup.
Any given IL-AQL notations shall be interpreted so that the number of defectives allowable for
acceptance is applicable separately to each test within a subgroup. However, the blank detail
specification may prescribe this same IL for relays submitted to cumulative tests of the same
subgroup.
2.6.3 Group C
The blank detail specification shall prescribe for each subgroup:
a) periodicity of each subgroup. If the same periodicity is applicable to all subgroups, it shall
be given at the beginning of the group test details;
b) the minimum sample size for each test (or group of tests) performed with the same relays
and the acceptable number of defectives.
2.7 Order of tests
Quality conformance inspection is divided into two parts: that carried out lot-by-lot, on which
the release of the individual lots is based, and that carried out on a periodic basis, which
contains the time-consuming and more expensive tests.
When several tests are subsequently to be carried out on any one specimen or number of
specimens, the following order shall apply, unless otherwise prescribed in the detail
specification:
a) a 100 % test with a screening or sorting function shall always precede any other non-
destructive (ND) or destructive (D) test;
b) tests in groups other than a 100 % test shall be performed in the sequence given in the
blank detail specification. It shall be ensured that the effects of earlier tests are not liable
to invalidate the results of the later tests (see 4.1).
3 Preparation of blank detail and detail specifications
3.1 Blank detail specifications shall conform to the test schedules given in Table 1 of this
specification and the related explanations.
3.2 Blank detail specifications shall give the following information or call for its inclusion in
the detail specification:
a) Identification of the detail specification.
b) Identification of the relay and information on its applications; identification shall be
provided by such properties as size, sealing, whether monostable or bistable, polarized or
not, or other characteristics required for identification, contact operating range and
temperature range.
c) Outline drawing of the relay and key dimensions; variants, such as for terminals, may be
given in an annex to the detail specification.
Customer packaging requirements for automatic handling.
d) Reference data of the relay.
1) A limited number of values is required on the front page to describe the overall
performance of the relay.
2) Full information in conformance with 1.4 and IEC 61810-1 shall be added on one of the
subsequent pages. Rated values preferably should be those listed therein. Where tests
refer to rated values, this shall be indicated with each test. Where tests are to be
performed at other than rated values, the test values shall be indicated and clearly
distinguished from the rated values.
e) Normative references.
Reference shall be made to IEC 61810-7 and this sectional specification. When reference
to further documents is necessary, such documents shall be listed with their full titles, year
of edition and, unless common knowledge, the source from which they can be obtained.
f) Assessment level.
Table 1 of this specification contains one test schedule. If additional tests not listed there
have been added, this shall be stated.
g) Periodicity of tests.
h) Formation of inspection lots, if predictable in the sense of 2.6.1.
i) Order of tests, if deviating from 2.7.
j) General test conditions, if deviating from 3.5 of IEC 61810-7.
k) Qualification approval test schedule.
l) Quality conformance test schedule.
For each group of tests, the final measurements and post-test requirements specified in
each of them may be summarized and stated at the end of the subgroup.
It shall be stated that samples subjected to destructive tests (D) shall not be released for
delivery.
– 12 – IEC 61811-50:2002 © IEC 2002
NOTE If application of SPC or ppm approach is required, this should be provided between the manufacturer
and user of a relay in accordance with CECC 00800, CECC 00016 or ISO 9001.
m) Specification of IL numbers (groups A and B) and sample sizes (group C).
n) Specification of AQL numbers (groups A and B) and acceptable numbers of defectives
(group C).
o) Marking of package and/or relays beyond those listed in this specification, if necessary.
p) Ordering information.
3.3 Additional information such as curves and drawings may be given in an annex to the
detail specification. Such information is not required to be verified for test purposes.
3.4 When preparing blank detail or detail specifications, the following procedures should be
followed:
– select the tests to be performed from Table 1 of this sectional specification;
– if necessary, add any other necessary tests, required or not specified in IEC 61810-7.
4 Test schedule
4.1 Test sequence
The order of tests in each subgroup of Table 1, and in the derived schedule in any
corresponding blank detail specification, is mandatory unless a specific statement to the
contrary is given. The sealing test shall always be the final test.
4.2 Types of relays, based upon environmental protection (relay technology RT)
RT 0 unenclosed relay
RT I dust-protected relay
RT II flux-proof relay
RT III wash-tight relay
RT IV sealed relay
RT V hermetically sealed relay
The definitions of protection and sealing are defined in 2.2 of IEC 61810-7.
4.3 Categories of application of contacts
CA 0 30 mV max./10 mA max.
CA 1 30 mV to 60 V/10 mA to 0,1 A
CA 2 5 V to 250 V/0,1 A to 1 A
CA 3 5 V to 600 V/0,1 A to 100 A.
The definitions of contact application are defined in 2.8 of IEC 61810-7.
The actual power rating of the contacts at minimum and maximum loads and the required
number of switched cycles shall be defined in the detail specification (see 4.4, note 3).

4.4 Notes relative to Table 1
NOTE 1 Test groups are as defined in IEC 61811-1.
NOTE 2 For the 100 % test subgroup, a relay shall be rejected when it fails any test. For detection purposes, a
contact can be considered closed when the voltage drop across it is less than one half of its open-circuit value.
Conditions of test shall be specified in the detail specification. All contact loads shall be at a level that does not
cause significant change to the contact surfaces.
NOTE 3 Electrical endurance testing shall be for a minimum number of operations as defined in the blank detail or
detail specification. If required, these tests can be continued to failure in order to acquire reliability data. Failure
criteria and rules shall be specified in the blank detail specification.
NOTE 4 For electromechanical all-or-nothing telecom relays, the majority contact action is break-before-make
change-over. To ensure that the contact sequencing occurs in this order, the transfer time measurement refers to
the time interval during which all contact circuits of a relay are open.
Analogously, to ensure that the make-before-break change-over contact sequencing occurs in the right order, the
bridging time measurement refers to the time interval during which all contact circuits of a relay are closed.
Specifying of time to stable closing in the detail specification is optional.
NOTE 5 Abbreviations:
M: mandatory test to be included in the blank detail or detail specification;
R: recommended test to be included in the blank detail or detail specification;
(D): destructive test;
(ND): non-destructive test.
5 Relay reliability – Failure rate data
The evaluation and indication of reliability data is not mandatory.
However, if required in a detail specification, the failure rate data for the reliability prediction
of telecom relays in electronic equipment (telecommunication systems, data processing, etc.)
shall be stated in an appropriate way. It is strongly recommended to give such data in
accordance with IEC 61709. Therefore, the preferred (blank) data base for failure rates, the
stress model and the particular stress factors for conversion of the failure rate data at
reference conditions to the actual operating conditions are given in informative annex A.
In the relevant detail specification, reference shall be made to this annex A and further details
shall be given.
The reference failure rate shall be determined by the manufacturer for his particular relay
type. The relay manufacturer is required to log cumulatively all endurance test data and all
other relevant data including those derived from field experience, which would demonstrate/
indicate achieved reliability. The endurance tests specified in the detail specification are
intended, amongst other things, to provide a measure of the failure rate under prescribed
conditions.
If another stress model, or other stress factors respectively, are known to be more suitable for
a particular relay type, such deviations shall be clearly described in an annex of the relevant
detail specification and used instead (all necessary details which allow the conversion of the
failure rate data to the actual operating conditions and the source(s) of these data shall be
described). However, the statements in Clause A.8 shall be kept in this case.
All the activities listed above shall be performed under the supervision of the National
Supervising Inspectorate (NSI).

– 14 – IEC 61811-50:2002 © IEC 2002
NOTE Relay manufacturers are not required to demonstrate the achievement of the failure rate data before
delivery of a specific lot.
Table 1 – Test schedule
Group A
Subgroup A0
For all tests in this subgroup: 100 % test. The lot shall be rejected in case of failure rate of
more than . % cumulative.
Test from IEC 61810-7 Options and particular requirements
Subclause
Visual inspection – relay marking (ND) R
3.6.4 a) and 3.6.4 b)
Coil resistance (ND) M
3.8.1
Dielectric test (ND) M
3.9
Contact-circuit resistance, static (ND) M Test voltage and current as for CA 0
3.12
Functional tests (ND) M Checking the relay function by monitoring
3.13 the contacts
Timing tests (ND) M See also 4.4, note 4
3.14.2
Sealing (ND) R Procedure 1 (test Qc, method 2), procedure 2
3.20.2 (test Qk, method 1 or 2) or procedure 4
(test Qy) for RT III and RT IV
Acoustic noise (ND) R Method 1, if stated in the detail specification
3.44  only
Table 1 (continued)
Subgroup A4
For all tests in this subgroup IL: S4
AQL: 0,25.1,0.4
Lot-by-lot
Test from IEC 61810-7 Options and particular requirements
Subclause
Visual inspection – relay marking (ND) M
3.6.4, items a) and b)
Coil resistance (ND) M
3.8.1
Contact-circuit resistance, static (ND) M Test voltage and current as for CA 0
3.12
Functional tests (ND) M Checking the relay function by monitoring
3.13 the contacts
Timing tests (ND) M See also 4.4, note 4
3.14.2
Sealing (ND) M Procedure 1 (test Qc, method 2), procedure 2
3.20.2 (test Qk, method 1 or 2) or procedure 4
(test Qy) for RT III and RT IV

Test from IEC 61810-7 Options and particular requirements
Subclause
Acoustic noise (ND) R Method 1, if stated in detail specification
3.44 only
Table 1 (continued)
Group B
Subgroup B1
For all tests in this subgroup IL: S3
AQL: 0,4.1,0.4
Lot-by-lot
Test from IEC 61810-7 Options and particular requirements
Subclause
Visual inspection – check of dimensions of M If applicable
stick magazines (ND)
3.6.1 and 3.6.4 a)
Visual inspection – other than marking, check of M
relay outside key dimensions (ND)
3.6.1 and 3.6.4 c) and 3.6.4 d)
Electrical endurance, miss-free acceptance (ND) R
3.30.5
Contact dynamic dielectric test (ND) R
3.50
Subgroup B2
For all tests in this subgroup IL: S3
AQL: 0,4.1,0.4
Lot-by-lot
Test from IEC 61810-7 Options and particular requirements
Subclause
Solderability (D) M If not tested in sub-group C1
3.25
– 16 – IEC 61811-50:2002 © IEC 2002
Table 1 (continued)
Group C
Subgroup C1
For all tests in this subgroup fixed sample size.
Period shall not exceed 1 year.
Test from IEC 61810-7 Options and particular requirements
Subclause
Magnetic interference (ND) R If stated in the detail specification only
3.37
Solderability (D) M For relays manufactured with automatic
3.25   facilities only, if not tested in subgroup B2
Electrical endurance (D) M Method 1, definition of contact fault and contact failure
3.30.3 and 3.30.4   in accordance with 1.3.3 of this specification

Subgroup C2
For all tests in this subgroup fixed sample size.
Period shall not exceed 1 year.
Test from IEC 61810-7 Options and particular requirements
Subclause
Acoustic noise (ND) R Method 1, only if not tested in A0 or A4
3.44 respectively
Dielectric test (ND) M
3.9
Impulse voltage test (ND) M
3.10
Insulation resistance (ND) M
3.11
Sealing (ND) R Procedure 1 (test Qc, method 2)
3.20.2
Table 1 (continued)
Subgroup C4
For all tests in this subgroup fixed sample size in accordance with Clause C.3 of IEC 60255-23.
Period shall not exceed 2 years.
Test from IEC 61810-7 Options and particular requirements
Subclause
Electrical endurance, extended assessment (D) M Method 1; prolongation of test from subgroup C1
3.30.6 or 3.30.3 and 3.30.4 possible,
definition of contact fault and contact failure in
accordance with 1.3.3 of this specification

Subgroup C5
For all tests in this subgroup fixed sample size.
Period shall not exceed 2 years.
Test from IEC 61810-7 Options and particular requirements
Subclause
Climatic sequence (D) M Dry heat, 3.15.2
3.15 Damp heat cyclic, 3.15.3
Cold, 3.15.4
Damp heat cyclic, 3.15.6
Damp heat, steady state (D) M
3.16
Robustness of terminals (D) M
3.24
Shock (D) M Method 1, functional
3.26 Method 2, survival
Vibration (D) M Method 1, functional
3.28
Mechanical endurance (D) M Method 2
3.31.3
Thermal endurance (D) M
3.32
Overload (contact circuit) (D) M
3.34
Magnetic interference (ND) R Only if not tested in C1
3.37
Resistance to cleaning solvents (D) M
3.47.2
Fire hazard (D) M Procedure according to IEC 60695-2-2
3.48.2
Table 1 (concluded)
Subgroup C6
For all tests in this subgroup fixed sample size.
Period shall not exceed 2 years.
Test from IEC 61810-7 Options and particular requirements
Subclause
Weighing (ND) M
3.7.2
Thermal resistance (ND) M
3.17
Rapid change of temperature (D) M Method 1
3.19
Resistance to soldering heat (D) M
3.25
– 18 – IEC 61811-50:2002 © IEC 2002
Annex A
(informative)
Data base for failure rates
A.1 Scope
This annex details the data base for failure rates of telecom relays based on IEC 61709. If
required in the relevant detail specification, the information given below and any further
details necessary should be given in a respective annex in that specification.
A.2 Description of the relay
A.2.1 Identification
The XY relay is (details to be given in the detail specification). For further details, see boxes
(5) and (6) under 1.3 of the relevant blank detail specification.
A.2.2 Ratings
Coil data and contact data see boxes (9), (10) and (11) under 1.3 of the relevant blank detail
specification.
A.3 Quality level
Form of qualification: IECQ qualification approval and quality conformance inspections
according to clauses 3 and 4 of this specification.
A.4 Fault and failure data
A.4.1 Fault definition
According to 1.3.3 and 1.3.4 of this specification – see also A.4.3.
A.4.2 Fault application
Useful life time period. Beginning of useful life time: relay in new condition; end of useful life
time: number of switching cycles stated in Table 3 of the relevant blank detail specification.
A.4.3 Failure definition
According to 1.3.3 and 1.3.4 of this specification.

Contact failure: contact-circuit resistance of a closed contact higher than 1 Ω, or resistance of
an open contact circuit lower than 100 kΩ, both more than once per 10 cycles (or for the
minimum number of switching cycles stated), calculated for each single contact; or a contact
fault due to non-opening with a short circuit between break and make contact (resistance
value lower than 100 Ω). This means that one contact fault is permissible for 100 000
switching cycles and seven contact faults are permissible for 700 000 switching cycles.
A.4.4 Failure application
Wear-out failure time period.
NOTE For conversion of the cycle-related to the time-related failure rate see E.2.2 through E.2.4 of IEC 60255-23.
A.5 Source of data
A.5.1 Failure rate under reference conditions λ specified in A.7
ref
Manufacturer’s laboratory tests in accordance with 5.2.1.2 of IEC 60255-23.
A.5.2 Stress factors π , π and π
ES S T
According to 7.7 of IEC 61709 – see A.10.
A.5.3 Data level
Single relay
A.6 Conditions for which failure rates apply
The application of the failure rates described in this annex is limited by the following values:
– ratings – see boxes (9) and (10) under 1.3 of the relevant blank detail specification,
– component climatic category according to IEC 60068 – see box (11) under 1.3 of the
relevant blank detail specification,
– operating range – see box (11) under 1.3 of the relevant blank detail specification,
– environmental data – see 2.6 of the relevant blank detail specification.
A.7 Reference failure rate λ
ref
A.7.1 The failure rate under reference conditions specified in A.7.2:
λ = . per operating cycle
ref
– 20 – IEC 61811-50:2002 © IEC 2002
A.7.2 Factors for failure rate under reference conditions
A.7.2.1 Time period
Mean failure rate related to wear-out time period according to C.3 of IEC 60255-23 (µ value)
with confidence level of 90 %.
A.7.2.2 Failure criterion
Fault and failure definitions according to A.4.
A.7.2.3 Operating mode
Accelerated conditions in accordance with E.1 of IEC 60255-23 simulating one operating
cycle per hour.
A.7.2.4 Climatic and mechanical stresses
Ambient temperature: 40 °C
Climatic conditions: 3K3 of IEC 60721-3-3
Mechanical stresses: 3K3 of IEC 60721-3-3
A.7.2.5 Electrical stresses
Stress region 2 according to figure 9 of IEC 61709: 0,5 V < U ≤ U , 0 A < I ≤ 0,1 A.

rat
A.7.2.6 Supplementary statements
No supplementary statements required.
A.8 Methods for combining and adding new data
The relay manufacturer shall cumulatively log all endurance test data and all other relevant
data
...