IEC TR 62500:2024

IEC TR 62500 ®
Edition 1.0 2024-05
TECHNICAL
REPORT
colour
inside
Process management for avionics – Highly severe stress tests for operating
margins identification and robustness improvement of avionics equipment –
Application guidelines
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IEC TR 62500 ®
Edition 1.0 2024-05
TECHNICAL
REPORT
colour
inside
Process management for avionics – Highly severe stress tests for operating

margins identification and robustness improvement of avionics equipment –

Application guidelines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-8322-8566-4

– 2 – IEC TR 62500:2024 © IEC 2024
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 Highly severe stress tests for margins research and robustness improvement –
Approach . 10
4.1 General . 10
4.2 Objectives . 10
4.3 Considerations . 11
4.4 General principles . 11
4.5 Example of the limitations of highly severe stress tests . 13
5 Industrial domains covered by highly severe stress tests . 14
6 Highly severe stress tests in the equipment lifecycle and associated stages . 14
6.1 General . 14
6.2 Design and development . 14
6.3 Qualification . 15
6.4 Production . 15
6.5 Operation and maintenance . 15
7 Planning and management of highly severe stress tests . 15
7.1 General . 15
7.2 Planning of highly severe stress tests and budget consideration . 16
7.3 Management of highly severe stress tests . 16
8 Typical methodology for implementing highly severe stress tests . 16
8.1 Basis for an effective approach . 16
8.2 Identification of equipment potential built-in deficiencies/weak points . 17
8.2.1 General . 17
8.2.2 Sources of information and data for identification of potential built-in
deficiencies or weak points . 17
8.2.3 Specific consideration of parameters related to intrinsic limits . 18
8.3 Selection of applicable stresses . 18
8.3.1 General . 18
8.3.2 Stress types . 19
8.4 Test plan and preparation of the tests implementation . 19
8.4.1 General . 19
8.4.2 Test plan contents . 19
8.4.3 Specific considerations . 22
8.5 Tests implementation . 23
8.5.1 General . 23
8.5.2 Checks before tests . 23
8.5.3 Stresses application . 23
8.5.4 Root cause analysis, corrective actions . 24
8.5.5 Test report . 25
9 Taking advantage and using experience gained with highly severe tests . 26

9.1 General . 26
9.2 Creating or enhancing a database . 26
9.3 Enhancing procedures and quality system . 27
9.4 Contribution to environmental stress screening (ESS) definition . 27
9.4.1 Reminder of ESS purpose . 27
9.4.2 Contribution of highly severe stress tests . 27
9.5 Checking the effectiveness of the highly severe stress tests with regard to
the experience and the equipment maturity by correlation with feedbacks . 27
9.6 Moving OEM’s culture forward . 28
10 Responsibilities and relationships . 28
10.1 Customer/OEM relationship . 28
10.1.1 Responsibilities . 28
10.1.2 Contractual requirements . 29
10.2 OEM and external test laboratories relationship . 29
11 Costs and savings . 30
11.1 General . 30
11.2 "Non-maturity" costs . 30
11.2.1 Cost due to delayed time to market (TTM) or poor entry into service (EIS) . 30
11.2.2 Cost of an in-service built-in deficiencies processing . 32
11.2.3 Cost of a in-service recovery operation and products retrofit. 32
11.2.4 Impact on brand image . 32
11.3 Expenses generated by the highly severe stress tests . 33
11.3.1 Engineering for highly severe stress tests preparation . 33
11.3.2 Highly severe stress tests implementation . 33
11.3.3 Weakened, damaged or destroyed equipment . 33
Annex A (informative) Highly severe tests approach . 34
A.1 Approach for highly severe stress tests . 34
A.2 Typical flowchart related to implementation of highly severe stress tests . 34
Annex B (informative) Examples of potential effectiveness of stresses with regard to

the nature of the equipment weak points . 36
Bibliography . 37

Figure 1 – Typical exploration of margins using a highly severe stress tests approach . 13
Figure 2 – Typical marketing stages of a product with time . 31
Figure A.1 – Typical flowchart related to planning of the highly severe tests . 34
Figure A.2 – Typical flowchart related to highly severe stress tests implementation . 35

Table B.1 – Examples of potential effectiveness of stresses with regard to the nature of
the equipment weak points. 36

– 4 – IEC TR 62500:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
HIGHLY SEVERE STRESS TESTS FOR OPERATING MARGINS
IDENTIFICATION AND ROBUSTNESS IMPROVEMENT OF AVIONICS
EQUIPMENT – APPLICATION GUIDELINES

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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IEC TR 62500 has been prepared by IEC technical committee 107: Process management for
avionics. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
107/411/DTR 107/415/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

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of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC TR 62500:2024 © IEC 2024
INTRODUCTION
In an increasingly harsh economic context (higher performance requirements, shorter
development cycles, reduced cost of ownership, etc.), consideration is given to rapid equipment
maturity, preferably from its entry into service (EIS).
It is with a view to remedying shortcomings that "highly severe stress" tests for margins research
and robustness improvement are considered in equipment design and development methods.
The main underlying principle behind this type of test strategy is as follows: rather than
reasoning in terms of conformity with a specification and applying tests in line with the
specification requirements, it is on the contrary attempted to push the equipment to its operating
limits by applying environmental stresses or stimuli, whose levels are higher than the
specification requirements.
PROCESS MANAGEMENT FOR AVIONICS –
HIGHLY SEVERE STRESS TESTS FOR OPERATING MARGINS
IDENTIFICATION AND ROBUSTNESS IMPROVEMENT OF AVIONICS
EQUIPMENT – APPLICATION GUIDELINES

1 Scope
This technical report considers the targets assigned to highly severe stress tests for operating
margins research and robustness improvement of avionics equipment, their basic principles,
their scope of application and their implementation process. It is primarily intended for avionics
programme managers, electronic equipment project managers, designers, test managers, and
dependability team.
This document provides guidance which can apply to all avionics programmes and is of primary
interest to the original equipment manufacturers (OEMs) in charge of designing, developing and
producing equipment built for these programmes, for obtaining early equipment maturity.
NOTE 1 Highly severe stress tests approach is often an industrial will in a global lifecycle cost effective approach
(see the Introduction) and it is not required at certification level. Moreover, customers can potentially define, in
contract clauses, in-service availability requirements, for example, from the entry into service (EIS) or in operation.
This highly severe stress tests approach is part of the avionics equipment design and
development stage, and it can address stresses in mechanical, climatic, electrical, etc.,
domains.
NOTE 2 The principles and objectives described in this document can apply to all types of equipment used in
systems developed in avionics programmes, whatever their nature (electronic, electromechanical, mechanical,
electrohydraulic, electro-pneumatic, etc.) and whatever their size, from "low-level" subassemblies (circuit card
assemblies (CCAs), mechanical assemblies, connectors, etc.) up to system level groups of equipment.
This document can be used in conjunction with IEC 62429, IEC 62506, or both, with regard to
dependability aspects related to equipment consisting of hardware with embedded software.
NOTE 3 This document can provide an aid in an equipment definition justification process (see CEN-CENELEC
prEN 9215) which can address:
• the development of a definition justification dossier (DJD) by bringing data related to equipment margins and to
decisions; or
• the justification of potential future changes made at equipment definition, for example when processing cases of
electronic component obsolescence.
For the purpose of this document, if the term "deficiency" is used alone afterwards, it is stated
as "built-in deficiency" or "weak point" and encompasses the concept of "deficiency and
associated potential malfunction or failure" (see 3.1.1).
Although developed for the avionics industry, this document can be used by other industrial
sectors at their discretion.
2 Normative references
There are no normative references in this document.

– 8 – IEC TR 62500:2024 © IEC 2024
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp

3.1.1 built-in deficiency
fault, flaw, imperfection, shortcoming or abnormality, often called weak point, in the design or
in the manufacturing processes of an item, which can potentially lead to a malfunction or a
failure and cause the item not to operate or function correctly
Note 1 to entry: Deviation from state-of-the-art design rules or inaccurate manufacturing process control can
constitute risks and be, for example, at the origin of equipment built-in deficiencies. These built-in deficiencies are
usually considered as weak points.
Note 2 to entry: The correction of a built-in deficiency goes in the direction of improving operating margin and
robustness of an item, and so in the direction of improving its early maturity.
Note 3 to entry: A built-in deficiency is usually latent (present or potential but not obvious or not explicit or dormant)
and manifests itself in operating time or certain conditions.

3.1.2
destruct limit
point from which an item breaks and suffers permanent and irreversible damage
Note 1 to entry: The destruct limit is above (beyond) the operating limit. The stress level leading to the destruct and
the permanent and irreversible damage is in excess of the one characterizing the operating limit of an item. The item
no longer functions, even the stress level is reduced and returned to below the one characterizing the operating limit.

3.1.3
highly severe stress test
test during which the equipment or some of its parts are submitted to environmental or operating
condition or stress that is increased progressively to values far in excess of the specified values,
up to the operating limit of the equipment
3.1.4
intermitent
occasional or irregular
Note 1 to entry: An intermittent malfunction or failure occurs occasionally or at irregular intervals.
Note 2 to entry: Intermittent malfunction or failure can occur at stress level in excess of the specified operating limit
of an item where the item functions with nominal load. The purpose of highly severe stress tests approach is to
precipitate the potential built-in deficiencies (at design or manufacturing processes level for example) into intermittent
or permanent malfunctions or failures to investigate them and seek corrective actions.
Note 3 to entry: Intermittent malfunction or failure origin can sometimes be detected by applying an additional
specific low stress level (vibrations for example) during a function test.

3.1.5
intrinsic limit
point below which an item, a material or a technology keeps its intrinsic properties or
characteristics, with respect to given condition(s) (for example, temperature, vibration, electrical
voltage, etc.)
Note 1 to entry: For example, melting temperature of a plastic, maximum junction temperature of a semiconductor,
yield strength of an alloy, etc., are intrinsic properties or characteristics of these materials or technologies.
Note 2 to entry: This limit, whether or not destructive, is an absolute barrier.
3.1.6
maturity
state of an item whose functional and operational performance can be considered stabilized
with respect to the specification
Note 1 to entry: Maturity is usually the result of a gradual process of eliminating built-in deficiencies still present at
the item level and its associated processes (manufacturing processes for example).
3.1.7
operating limit
point at the boundary of the operation area of an item where it still operates or functions
correctly and beyond which it no longer operates or functions correctly
Note 1 to entry: The operating limit defines the maximum range of correct operation area of an item, and it is usually
characterized by stress level above which the item no longer operates or functions correctly. Usually, for determining
this stress level, the stress level at which the item no longer operates or functions correctly is reduced to verify if the
function of the item resumes; if the functionality resumes at the reduced stress level, then this stress level
characterizes the operating limit.
Note 2 to entry: The operating limit can correspond to the intrinsic limit of a technology. In this case, this is the
maximum range of operation which can be reached by the equipment.
3.1.8
operating margin
difference between the operating limit and the nominal operating level under specified stress
levels
3.1.9
robustness
property of an item having reduced sensitivity of its performance under, for example, the
environmental conditions, to components variations, or to drifts in its manufacturing processes
Note 1 to entry: Robustness is usually the result of actions taken to obtain sufficient operating margins while at the
same time reducing all forms of variability.
3.2 Abbreviated terms
CCA circuit card assembly
CDR critical design review
EIS entry into service
EMC electromagnetic compatibility
ESD electrostatic discharge
ESS environmental stress screening
LCD liquid crystal display
MTBF mean operating time between failures
OEM original equipment manufacturer
PCB printed circuit board
PDR preliminary design review
– 10 – IEC TR 62500:2024 © IEC 2024
RTV rapid temperature variation
TTM time to market
4 Highly severe stress tests for margins research and robustness
improvement – Approach
4.1 General
With regard to the initiative for obtaining early equipment maturity, the approach based on highly
severe stress tests for operating margins research and robustness improvement consists in
submitting an equipment or some of its component parts to environmental or operating stresses,
or both, which are gradually raised to values in excess of the specified values until the
equipment operating or destruct limits are reached.
Instead of reasoning in terms of conformity with the specification (which is representative of the
equipment real lifecycle or mission profile), the highly severe stress tests approach aims,
indeed, on the contrary with a view to obtaining robust and mature equipment, to push the
equipment to its operating limits or potentially to its destruct limits in order to:
• detect potential intermittent or permanent malfunctions or failures that were not foreseen
before the tests;
• reveal, identify and then, depending on margins targets if defined, correct built-in
deficiencies which can lead to intermittent or permanent malfunctions or failures; and
• explore available margins and improve, if needed, these margins through appropriate
actions, for example, on the equipment design itself or the manufacturing processes.
Equipment operating margin targets are often defined to orientate the highly severe stress
approach.
NOTE For example, if not specified by the customer, an operating margin target of 5 °C can be defined with regard
to the specified low operating temperature, T , of an equipment; so, in this case, the highest level of stress is
op-low
limited to T -5 °C. The equipment operating margin target can also be defined according to the industrial usage
op-low
or application domain or by experience feedback.
Usually, the highly severe stress tests activity is part of a global lifecycle cost effective approach
and is formalized with its general objectives and principles in quality system procedures or other
specific summary documents, allowing effective coordination and OEM executive officers'
support.
Annex A, Figure A.1, provides a typical flowchart related to the highly severe stress tests
approach.
4.2 Objectives
The main objectives of the approach include:
a) achieving, in a relatively short time, an early equipment maturity by improving its robustness
toward the specification;
b) taking, from the first prototypes, full advantage of technologies and manufacturing
processes, by:
– eliminating, for example, design and manufacturing processes built-in deficiencies;
– researching operational limits or destruct limits in operating and environmental
conditions more severe than the specified ones;
– considering operational margins allowing to:
• satisfy, for example, potential technologies or manufacturing processes variations
(which can lead later to potential malfunctions, failures or specification non-
conformities);
• establish design provisions for potential future specific changes, for example, to
facilitate (if possible) minor specification evolution or management of electronic
component obsolescence with potential alternatives, in particular, with regard to
future equipment maintenance management;
c) contributing potentially to the lifetime of the equipment in service through its conditions of
use;
d) contributing to specify optimal or more accurate environmental stress screening profiles;
e) reducing the global costs of ownership (see Clause 11).
NOTE These objectives rely, as mentioned in 4.1, on:
• detection of built-in deficiencies as early as possible (so that they can be more easily corrected without excessive
cost), as these deficiencies can be present, for example, in design errors or imprecise controls of the
manufacturing processes;
• exploration of the operating limits once built-in deficiencies have been eliminated or corrected; these limits can
be pushed back through design changes, for example, when the margins with regard to the specified operating
range appear insufficient or inadequate.
4.3 Considerations
A highly severe stress test can be characterized as follows:
• A highly severe stress test is a proactive type of test: it is considered as a "tool" to support
the design and development of the equipment, and its manufacturing processes
implementation. It usually leads to engineering activities aimed at understanding the
potential observed malfunctions or failures mechanisms and the built-in deficiencies origins
which caused them, in order to consider then the corrections technically and economically
feasible; these corrections enable to eliminate or correct built-in deficiencies, or at least to
delay significantly their manifestation with regard to the margins which are considered
acceptable. The highly severe stress test is "proactive" in that it encourages these
engineering actions at the earliest stage in equipment development.
• A highly severe stress test is not a conformity test: through the desire to explore the margins
and expand them if necessary, the highly severe stress test looks above all to reveal the
equipment built-in deficiencies and their associated malfunctions or failures when working
beyond the specifications. It is, therefore, the opposite of a conformity test, which aims to
ensure that the equipment performance is correct when it is subjected to the specified
operating and environmental conditions.
• A highly severe stress test is not confused with a "conventional" accelerated lifetime test:
the purpose of an accelerated lifetime test is in fact to predict the evolution of the behaviour
of an equipment in its operational conditions of use, by subjecting it to stresses that are
harsher than the values expected during its lifetime profile. To do this, the "conventional"
accelerated lifetime test relies on analytical equipment failure mode acceleration models,
which is not the case with the highly severe stress test.
• A highly severe stress test does not produce reliability measures: as the highly severe stress
test works outside the specified domains, the analytical acceleration models can no longer
apply to the domains explored. Furthermore, it is very hard to involve the "time" factor given
the very short duration of the test. The result is that as things currently stand, the highly
severe stress test cannot be used to estimate equipment reliability or lifetime characteristics
in the specified conditions of use.
4.4 General principles
As a "tool", the highly severe stress tests aim – through application of stresses going beyond
the specification or simply not specified – to stimulate potential built-in deficiencies in the
equipment design and in its manufacturing processes. Revealing these deficiencies, and the
associated operational malfunctions or failures, is thus an opportunity to improve the equipment
or processes more quickly than with a traditional approach, leading to an expansion of the
operating margins and contributing to greater maturity.

– 12 – IEC TR 62500:2024 © IEC 2024
It is understood that in a highly severe stress tests approach, the stresses are applied to actively
stimulate the potential weak points of the equipment and its processes and are not, therefore,
designed to simulate the conditions of use of the equipment during its lifetime or mission profile.
These stresses are applied either alone or sometimes combined, exceeding the values
expected during the lifetime of the equipment, until reaching the equipment operating limit and
potentially the equipment destruct limit, or the intrinsic limit set by the technologies. This implies
gradually eliminating the various barriers preventing this limit from being reached and which
are due to the existence of any built-in deficiencies still present. An essential goal of the highly
severe stress tests is precisely to reveal the existence of these deficiencies, to eliminate or
correct them and to restore operating margins if needed.
NOTE 1 Some stresses can be chosen according to potential weak points which are identified initially.
Among the reasons which justify the desire to correct built-in deficiencies, the following can be
mentioned:
• the experience gained by OEMs which use highly severe stress tests shows that most
problems detected during these tests would appear and be detected in the field if the built-
in deficiencies revealed by these tests are not eliminated or corrected;
• experience shows that built-in deficiencies can often be located and can be eliminated or
corrected or attenuated both easily and economically (for example: inadequate footprint of
an electronic component package leading to poor solder joints, inadequately tightened
screw, electronic components mounted on vibrating parts of a CCA, CCA inadequately
fastened in an equipment subject to vibrations, etc.).
Because of its damaging nature, the principle of the highly severe stress test is often thus a
cultural change in relation to the traditional approach whose main aim is to ensure the
conformity of equipment performance within the specified conditions. As shown typically in
Figure 1, the accelerated stress test aim is no longer to show that the equipment is in
conformity, but to prove that exploration has been conducted beyond the specified frontier in
order to clean the equipment of built-in deficiencies limiting its potential robustness, potentially
going up to the intrinsic limit set by the technologies.
NOTE 2 Performing a highly severe stress test does not lead to over-sizing or over-design. The ultimate purpose
of the accelerated stress test is to track down and eliminate built-in deficiencies, which by principle are, for example,
the result of non-compliance with, or ignorance of, the state-of-the-art rules or good practices (in design and
manufacture). These actions are, therefore, dedicated to eliminating built-in deficiencies, contributing to improving
the operating margins and obtaining higher robustness. Generally speaking, one does not attempt to push back the
fundamental limits of the technologies, components or materials, which would call into question the design and
development choices, entailing probably significant additional investment and time.
NOTE 3 An important aim of a highly severe stress test is to eliminate the weakest links in the product, making all
parts equally strong or robust in relation to the environmental loads and satisfying the operating margins target, To
avoid overdesign the aim is not to make the whole product as strong as possible since that would most likely increase
costs and weight for example but each malfunction or failure observed is carefully investigated and evaluated to
determine if it can occur in the field; the reason is that the highly severe stresses can activate malfunctions or failure
modes and the aim is that they do not occur in the field.

Key
Specified domain: described in the equipment Technological area: this corresponds to the

specification. ideal equipment, designed and produced
without error, but which represents the intrinsic
limit of technologies, and defines the maximum
operating margin with respect to the
specification.
Domain revealed by the highly severe stress tests: Growth in operating margin by gradually

this corresponds to the real limits of the equipment, as increasing the stresses and correcting the built-
revealed by the highly severe stress tests. The stars in deficiencies revealed.
bordering this domain correspond to built-in
deficiencies detected, causing the equipment to cease
to operate or function at this stress level. The limits
reached can potentially correspond to destruct limits.
Built-in deficiencies (to be detected and
eliminated or corrected).
Figure 1 – Typical exploration of margins using a highly severe stress tests approach
4.5 Example of the limitations of highly severe stress tests
Despite its efficiency and speed, the highly severe stress tests method has, nevertheless, some
limitations which can, in certain cases, require to consider first specific testing or specific
checking of equipment components.
In practice, and independently of the parameters that highly severe stress tests do not address
by their very nature (such as electrostatic discharges (ESDs), sealing, etc.), they provide
relatively few information about the robustness of equipment that can change over time as a
result of internal physical-chemical reactions for example.

– 14 – IEC TR 62500:2024 © IEC 2024
The issue of electro-migration in ceramic capacitors is considered as an example of such a
limitation:
• This effect causes, ultimately, capacitors to fail as a result of short-circuiting, which can
take two weeks or two years to occur, depending on their design, their manufacturing
process and the environmental conditions under which they are used.
• Highly severe stress tests of a new manufactured equipment cannot always reveal this type
of fault, because at the time of testing, the ceramic capacitor complies fully with its
specification and these tests only marginally accelerate the latent electromigration effect.
• In this example, at in-coming stage, integrity check of the supplied capacitors can
considerably reduce the risk involved. Such check usually involves specific humidity and
temperature testing of ceramic capacitors, using test conditions which can be impossible to
reproduce with tests at the finished equipment level.
On the basis of this example, OEMs' feedback and experience enable the OEMs design
authority, or the program or project manager for example, to decide whether the highly severe
stress tests defined in the design and development phase, or the screening tests defined in the
production processes, are sufficient. If not, OEMs can design, evaluate and implement
additional filters to achieve the desired degree of robustness.
5 Industrial domains covered by highly severe stress tests
The highly severe stress tests can apply, beyond avionics, to all industrial sectors and to various
equipment categories (for example: electrical, electronic and electromechanical equipment),
provided that the most pertinent stresses (mechanical, climatic, electrical, etc.) are used with
respect to the composition of the equipment (electrical, electronic, mechanical parts, etc.).
In some cases, the highly severe stress tests are not suitable for small equipment or very large
equipment; IEC 62506 can provide information.
The equipment is able to be monitored for function during the highly severe stress tests either
continuously or during pauses in the step stress process.
6 Highly severe stress tests in the equipment lifecycle and associated stages
6.1 General
To ensure optimum efficiency, the highly severe stress tests approach fits into the equipment
lifecycle potentially at different stages and it is preferable to consider it as far upstream as
possible in the lifecycle and the decision-making process, keeping in mind that the later a
problem is detected and a change is late, the higher the cost is.
The highly severe stress tests approach therefore entails availability of equipment for the tests
(prototypes for example) (see 6.2).
6.2 Design and development
The highly severe stress tests are an essential activity of the design and development stage in
view of early equipment maturity from the EIS.
These tests are usually implemented on equipment which is operationally representative of the
final equipment. This includes at least:
• very close definition and configuration of the final equipment;
• production processes closely representative of the series production ones.

Highly severe stress tests are usually considered as a supplement to the equipment validation
and verification processes for addressing the equipment robustness improvement and margins
identification.
NOTE 1 The objectives of the validation and verification processes, as well as associated activities are indeed to
ensure that the requirements identified in the technical specifications are correctly impleme
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