2 January 2003: Add new source for Recommendation nº400 Installation + Zoning (below).

3 January 2000
Source: http://www.scssi.gouv.fr/document/tempest.html (FR)

Rough translation by Cryptome with Systran. A better translation would be appreciated: jy@jya.com


Recommendation nº400 Installation + Zoning (below)

Other documents listed (but not available):

II nº300bis General instructions
Directive nº485 Installations
Directive nº495 Zoning
Guide nº480 Politics of TEMPEST
Guide nº460 Inspection & Quality Control
Report nº490 Material and Equipment

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Service Central de la Sécurité des Systèmes d'Information

N° 400/DISSI/SCSSI le 18 octobre 1991



Interdepartmental Delegation for information system security



This document describes the protection of information systems against the threat caused by the emission of compromising signals by conduction and radiation. Its aim is to define the technical rules of security applicable to the installation of hardware or automatic data processing systems.

These technical rules aim at guaranteeing the confidentiality of classified information affecting national security, primarily by limiting the emission of compromising signals generated during data processing.

The effectiveness of required protection will be greatest when the measurements specified by this recommendation are used in conjunction with the use of hardware which complies with standards of electromagnetic compatibility in effect, in particular standard NF 98 020 applicable to information processors.



1.1. Interfering signals
1.1.1. Origin and definition
1.1.2. Mode of emission
1.1.3. Coupling
1.1.4. Compromising emanations

1.2. Compromising electromagnetic radiation

1.2.1. Definition
1.2.2. Protection against compromising electromagnetic radiation

1.3. Compatibility of electromagnetic radiation

1.3.1. Definition
1.3.2. Development of compatible hardware General considerations Equipment Shielding Filtering Cables Grounding


2.1. Objective

2.2. Limitation of emission by conduction

2.2.1. Cables and unintended conductors
2.2.2. Interruption of metal continuity
2.2.3. Grounding The ground well (puits) The connecting conductor Network of ground conductors

2.3. Limitation of emanation by radiation

2.3.1. Use of a Faraday cage
2.3.2. Adjustment of zones of protection Electromagnetic zone of security Zone of coupling

2.4. Zoning of a building

2.4.1. Zoning of installations
2.4.2. Measuring attenuation of buildings
2.4.3. Interpretation of results
2.4.4. Example of procedure


3.1. Certification of installations:
3.1.1. Descriptive file Overall plan of the site Plan of the building Nature and characteristics of equipment processing classified information

3.1.2. Measurements file
3.1.3. Synthesis file

3.2. Maintenance of installations

3.3. Quality control of installations


1 - List of national standards
2 - Network of ground conductors
3 - Installation zoning standard


1.1. Interfering signals

1.1.1. Origin and definition

Any hardware or system which processes or transmits information in electronic form is a source for transient electromagnetic disturbances. These disturbances, compromising emanations, are caused by variations of stable electronic states of the various circuits which the hardware activates during its operation.

1.1.2. Mode of emanation

Generally the interfering signals appear in the forms of:

- electromagnetic waves which are emitted by radiation into surrounding space;

- currents of conduction which are emitted along various conductors connected to the hardware involved.

Most of the time there is interaction of these two forms of emanation. The radiated disturbances cause currents induced in the conductors connected to the hardware or located in its vicinity such as feeders, transmission lines or unintentional conductors (heating pipes, water pipe, concrete-reinforcing steel, etc...).

In the same way an unarmored conductor which conveys disturbances can serve as a transmitting antenna and in its turn transmit to elements in the surrounding space.

1. 1. 3. Coupling

When there is passage of energy between two circuits these circuits become coupled circuits. Among the many processes of coupling one can distinguish two which are fundamental:

- common impedance coupling;

- magnetic coupling.

Common impedance coupling occurs when a circuit is a common part of the source of interference. Common impedance can be any element of the circuit, resistance, capacity, ground return, feeders, etc... In this type of coupling, the passage of energy between the two circuits is done by conduction.

Magnetic coupling results from the mutual inductance of two circuits placed in the vicinity one of the other. In this case the passage of energy into the circuits is done by radiation.

1.1.4. Compromising emanations

Among all the interfering signals generated during the operation of the equipment, there are some which are representative of the processed data. Their interception and analysis are likely to allow the reconstruction of information. These signals, are called "compromising emanations."

1.2. Electromagnetic emanations

1.2.1. Definition

Electromagnetic emanations can be defined as being the revelation of confidential information to persons who are not authorized to know it. This illicit interception of information is carried out by the intermediary of compromising emanations. Information represents the generating phenomenon and the compromising emanations the resulting phenomenon; the exploitation of the correlation between the compromising emanations and the processed data allows, beginning with knowledge of the processed phenomenon, to reconstruct the generating phenomenon.

The correlation between compromising emanations and information can appear under various aspects. Generally, when it is translated at the electronic level, information arises in the form of a chart of a succession of impulses, each one being representative of a dual change of stable state of the set electronic state. These changes of successive states cause in the various circuits of the equipment under evaluation characteristic disturbances which have a direct relation to the impulses themselves. The disturbances can occur either during the impulse increase or its decrease, and they can also be generated with each change of the impulses. If information is exploited in parallel state the generated elements have, moreover, a simultaneous amplitude proportional to the pulse repetition frequency.

Exploitation of the disturbances, i.e. the knowledge of their relative positions, and their intensity, makes it possible to recreate impulse images to match those at the origin of these disturbances and consequently reveal the data which are processed. The interception and exploitation of the compromising emanations of the knowledge of the processed data constitute electromagnetic compromise.

1.2.2. Protection against electromagnetic compromise

Protection against electromagnetic compromise is obtained while using:

- materials are protected against the emission of compromising emanations by being installed according to particular rules;

- materials are not protected but installed according to rules appreciably more severe.

Materials protected from the emission of compromising emanations are materials which comply with particularly stringent military standards whose application is reserved to governmental users because the processed data concerns National Defense or the security of the State and are classified within the meaning of decree n° 81-514 of 12 May 1981 relating to the organization of the protection of secrets and information relating to National Defense and the security of the State.

These materials result from processes of development where the objectives of security are taken into account as part of their design and call upon components and technologies which are adapted to them.

For protection against the electromagnetic compromise of classified information affecting the national security, it is recommended the use of materials of strength complying with the standards of electromagnetic compatibility in conjunction with installation rules defined in chapter 2.

1.3. Electromagnetic compatibility

1.3.1. Definition

Electromagnetic compatibility (EMC), according to the definition given it in French standard NF C 98020, is the capability of a device, apparatus or a system to function in a satisfactory way in its electromagnetic environment without itself producing unacceptable electromagnetic disturbances in other materials, apparatuses or systems.

EMC results from the reduction and the control of the interfering signals of electronic origin. The objective pursued by the EMC remains mainly directed towards the harmonious insertion of equipment or system in an existing medium in order to obtain the weakest possible functional interaction between the medium and the equipment.

From this point of view, viewed at the level of the equipment, EMC represents the resolution of problems arising from the electronic interactions.

Within the meaning of EMC, an interference is an electric disturbance created by one part of a unit and transported to another part which obstructs its operation. These interactions can appear either inside the equipment or outside it.

The field covered by the EMC is extremely wide and extends to all electronic equipment of industrial, scientific and medical (ISM) facilities to domestic equipment. It also relates to automatic data processors (ADP).

The field of the EMC is based on a regulation developed by national and international organizations whose principal ones are:

- the IEC (International Electrotechnical Commission) and its Committees of Study;

- the CISPR (Special International Committee of the Radioelectric Disturbances);

- CENELEC (Electrotechnical European Committee for Standardization).

The role of these organizations comprises for a great part the development of standards specifying:

- acceptable limits for disturbing emission;

- limits for the sensitivity (immunity) of materials (victims).

Appendix 1 presents a list of national standards.

1.3.2. Development of compatible materials

The fundamental objective of EMC is the harmonious insertion of an electronic component in its environment in order to obtain the weakest possible functional interaction. EMC is not concerned with that correlation which could exist between possible disturbances and the processed data. General considerations

The reduction of the interferences generated by equipment requires a comprehensive process and the problem must be dealt with as a whole from the design stage to the manufacture and the installation of the equipment. The techniques used to reduce the interferences relate at the same time to the internal parts of the equipment, shielding, filtering, connecting cables and grounding. The equipment

The reduction of the level of the interferences requires that when designing equipment, a study is undertaken to obtain the data necessary to make it possible to determine the sources of interferences, to eliminate or reduce some of these sources and finally, to understand the remaining sources.

The reduction of interferences is accomplished mainly by a judicious choice of components. Generally, components containing technology known as fast, i.e. presenting very short durations of commutation, revolving machines and electrical feeder circuits should be guarded against as generators of disturbances. Shielding

The practical method most effective to attenuate, or to even remove, circuits coming straight from a source consists in inserting a shielding between the transmitting body and the receiving body (in the broad sense of the term). A good shielding must prevent the signals created to come out of an enclosure or to reduce them sufficiently so that they cannot disturb the operation of nearby equipment. In the same way, good shielding must prevent a sensitive apparatus from receiving undesirable signals which surround it and which would harm its proper operation.

If shielding is placed to block a circuit radiated by a source, this screen causes a weakening of radiated energy, which is a function of the effectiveness of shielding and which corresponds to the sum of the losses by reflexion and absorption.

These two elements depend on the type of radiation. The reflexion increases with the frequency in magnetic field and decreases in electric field. Absorption increases with the frequency, the permeability of a material and its thickness.

The search for an optimal shielding thus requires one to know the precise range of frequencies in which one works, impedance of the electromagnetic wave that one wants to attenuate, the distance between the source and shielding and the material that one will use.

As an example, protection against the magnetic fields low frequency and low impedance (weak field) implies greater thicknesses of shielding and/or the use of material of high permeability.

It should however be stressed that the effectiveness of a shielding depends above all on treatment of penetrations specified here. Filtering

Any equipment, for its operation, is necessarily connected to the environment, other equipment, energy source as well as to the ground. In the absence of particular protection, these connections represent access paths for undesirable disturbances.

The interactions due to conduction can be removed by the use of filters whose role is to allow passage only of acceptable signals. One distinguishes two kinds of filters:

- passive filters: They generally consist of resistances, inductances and capacities. These components can be combined in various ways according to the required goal. These filters do not require energy. Their use is primarily directed towards analogical applications of low frequencies (telephone, intercom, energy...).

- active filters: These filters are made up in general of operational amplifiers and optoelectronic couplers, and require energy. They have the advantage of allowing a discrimination of the interfering signals inside their operating range thanks to a threshold of release. Their employment is strongly recommended for the transmission circuits of data.

Filtering can also be obtained by the use of optical fibres in particular in the case of penetrating walls of Faraday cages for circuits other than those of energy.

For unintentional conductors such as metal pipes or drains, it is recommended to stop electrical continuity by the insertion of an isolating sleeve placed at the perimeter of the zone of coupling. Connecting cables

In addition to its essential function which consists in ensuring the transport of energy between two points, any conductor, whether internal to equipment or external and inter-connecting several pieces of equipment, behaves like a vehicle of interferences. These interferences can be collected by the conductor, which then plays the part of receiver. They can also be reflected by the conductor either by electromagnetic radiation or by conduction. The conductor then plays the part of a transmitter.

The solution which makes it possible get rid of interferences in conductors, consists in decreasing the sensitivity of the cables to the unacceptable effects of electromagnetic fields. For that, it is advisable to use:

- shielded cables: the shielding can surround the disturbing cable as well as the disturbed cable.

- symmetrical lines: at the two ends of the symmetrical lines one uses transformers of connections connected to the ground by the mid-point of their secondary. That makes it possible to isolate the subsets between them and limit the increase from tension above the potential of the ground. One thus eliminates the tensions and the currents induced by the disturbance fields.

- twisted pairs: the twisted pairs have the advantage of reducing the surface of the circuit what limits the electric loops and removes the undesirable effects of the magnetic fields.

- optical fibres which are insensitive to electromagnetic fields. Grounding

The first reason for grounding of equipment is staff safety. The objective of this grounding is to avoid dangerous tensions in the equipment for the personnel suitable for handling them during operation.

Grounding allows, moreover, to decrease the couplings by the common ground what, by repercussion, supports the reduction of the interferences.

The ground connection of an electronics component can be carried out in three manners:

- system with multiple grounds: this method has the advantage of decreasing the impedance resulting from the ground what reduces the resistive coupling between equipment. It requires in against part the existence of an equipotential surface of reference for the unit.

- floating system: this method makes it possible to deal with equipment completely isolated from the environment and any source of inopportune disturbances. However, because of defects of consecutive insulation to the creation of static heads or tensions of defect, it can be the seat of dangerous important tensions for the personnel.

- system at only one point of ground: only one point is used as reference to all the unit. This reference must then be distributed using conductors with low resistance. This method makes it possible to reduce ground currents which are sometimes sources of disturbances.


2.1. Objective

The rules of installation described in this chapter aim to reduce the risks of disclosure of classified information, during their exploitation, by best limiting possible propagation by conduction and radiation of the interfering signals caused by the equipment used.

2.2. Limitation of emission by conduction

The limitation of emission by conduction of compromising signals requires that physical measures are taken:

- on the level of the cables, powerlines, telephone lines and unintentional antennas located in the environment close to the equipment;

- on the level of all the antennas connected to the equipment or system used;

- for the connection of the equipment to the ground.

2.2.1. Unintentional antennas and cables

All cables located in the environment close to the equipment used for the classified data processing which cannot be moved apart from the zone of coupling (cf paragraph must be filtered. It is advised to use for this purpose filters which present a bandwidth adapted to the characteristics of the useful signal circulating on the cables and an attenuation raised apart from this level of frequencies.

Among the cables concerned with this filtering one can quote in a nonrestrictive way:

* cables connected to the equipment
- line of transmission
- line of remote control
- feeder

* cables not connected to the equipment

- powerlines
- telephone lines
- all metal lines likely to be used as unintentional antennas.
2.2.2. Interruption of metal continuity

Water piping, central heating and ventilation ducts located in the immediate vicinity of equipment can support conduction of compromising emanations generated by the equipment during its operation. A way of protecting against this threat consists in stopping their metal continuity by interposing in the various pipes an insulating flange, generally out of Teflon, of a score of centimetres length in limit of the zone of coupling. This provision breaks the electrical continuity of piping and avoids the emanation of compromising signals by conduction.

2.2.3. Grounding

Grounding of any electric component is essential mainly for reasons of safety of the people vis-a-vis the electrical dangers. It also plays an important part, in particular in the field of the high frequencies, when it is a question of running out of the interferences to the mass. A defective grounding installation or one not in conformity risks producing the opposite effect of that sought, and will prove to be dangerous as well in the plan for personnel safety as in the plan for information security.

Grounding of equipment, according to codes of practice, is done through grounded circuit, detailed hereafter, whose components are:

- the ground well;
- the connecting conductor between the well and the equipment;
- the network of ground conductors which distribute potential zero to the equipment. The ground well

The ground is considered in theory the point of zero reference of the potential. The ground well is the place where the electrical contact between the ground is established - ground - and the installation. The quality of this contact mainly depends the value on the ohmic resistance presented by the ground.

The requirement of safety of the people requires the unicity of the ground well. The safety of information implies a ground of good quality, located in a controlled place. Various methods of realization of the grounds make it possible to achieve these goals; these methods are developed in the GAM T 22 guides practical for the realization of the grounds and masses.

############################################ The connecting conductor

The connecting conductor makes it possible to connect the material to the ground well. On this conductor, circulate of the interfering signals generated by the material. This fact it presents a certain vulnerability. To cure it, the ground conductor must be located in a controlled zone (with the physical direction access). If this protection cannot be ensured, it is recommended to place the ground conductor in a metal sheath whose role is to prohibit any connection. This metal sheath must be installed under the following conditions:

- insulated from the connecting conductor;
- not connection with the ground well;
- connection on the level of the equipment.

The ground conductor must be provided with a bar of cut, located near the ground well. The role of this bar of cut is to allow the measurement of the impedance of the ground well. Within the framework of the information system security, it is advised to have a ground having an impedance lower than 5 ohms. Network of ground conductors

It often happens that in the same building various categories of materials their grounding requires:

- electric materials of power and constraint (elevators, air-conditioners...;
- materials of data processing;
- low instrumentation and measurements level;
- equipments of telecommunications.

It is advised to use as many conductors of ground connection than there are categories of materials. The whole of these ground conductors forms a network of conductors. It is then imperative that the network is connected to the ground well in only one point. Generally, the various ground conductors are connected to a case located at more close to the ground well. Each conductor has a bar of cut. The case is connected to the ground well by a connection as short as possible and which has an impedance as low as possible. This connection is also provided with a bar of cut. Appendix 2 shows an example of realization of connection of network of ground conductors.

2.3 Limitation of the propagation by radiation

The limitation of the propagation by radiation consists:

- is to be confined, artificially, the interfering signals in a given volume and to take particular measures so that they do not come out of there. It is the case when one installs equipments of treatment in a Faraday screen room;

- is to be arranged, around the equipment, of the zones in which provisions are taken in order to prevent the capture of the compromising interfering signals. Dimensions of these zones are given so that the signals which would be collected apart from those would not have any more one sufficient amplitude allowing their exploitation.

2. 3. 1. Use of a Faraday cage

The Faraday cage room is an armored enclosure, made up of metal walls on its six faces. The shielding behaves as an electromagnetic screen which prevents electromagnetic wave emanation. The weak points of a Faraday cage are the openings which it is advisable to correctly treat in order not to degrade the total characteristics of weakening of the cage. These openings are primarily;

- the door;
- openings, necessary to ensure the ventilation and the air-conditioning of the room;
- passages of cables to connect the materials exploited in the cage with the external environment (lines of transmission, cage power supply in electric power, offset of alarm...).

All the connections penetrating the wall of the cage must be provided with adequate filters. The use of optical fibres to convey information out of the cage are the best solutions because the optical fibre is insensitive to electromagnetic radiations.

Grounding of the Faraday cage is carried out starting from a single point located on the external wall of the cage. The materials located inside the cage are connected individually, directly on the internal wall of the cage or well on a bar of connection connected to the cage.

2.3.2. Adjustment of zones of protection

When the material used for the data processing is not installed in a Faraday cage, it is necessary to surround it by a zone of protection which comprises an electromagnetic zone of security and a zone of coupling as defined below. At the end "zone" is attached a concept of spherical volume centered on each equipment. Electromagnetic zone of security

The electromagnetic zone of security is a zone in which permanent measures are taken to detect and prevent any electronic surveillance, searches for information or installation of surveillance devices. It is appropriate, also, that particular precautions are taken to control movements of personnel, including vehicles.

The effectiveness of such a zone grows with its dimension. A distance of 100 meters is recommended taking into account the current possibilities for analysis of compromising emanations. Zone of coupling

The zone of coupling is a zone which should not comprise equipment or superfluous circuit (telephone, intercom.) likely to collect by coupling of the compromising interfering signals coming from the equipment processing the classified data or the circuits conveying this information. The circuits which come out of the zone of coupling must be filtered and armored. In this case, the filters are placed in limit or apart from the zone; the shielding of the circuits is at least a minimal distance of three meters.

This zone must be as as possible free from objects likely to behave, even unintentionally, as conductors or amplifiers of compromising emanations. It is recommended to avoid the installation of equipment processing the classified data near metal objects or furniture (heating radiators central, cupboards... which can amplify the emanations), which increases the distance from emission. If these objects cannot be eliminated, their metal continuity must be stopped, as indicated in paragraph 2.2.2, by an insulation idoine placed at the zone's perimeter or beyond.

The more the dimension of the zone of coupling increases, the more the possibility of reinduction of the compromising emanations by coupling decreases, the more installation of such a zone becomes difficult taking into account the problems of infrastructures which are posed. It is however recommended to plan for zones of coupling of at least 5 meters distance, centered on the equipment.

2.4. Zoning of a building

The principle of zoning of a building consists in determining, inside this building, of the zones which present, for the electromagnetic emission, of the levels of weakening located in a given range. Each zone is thus characterized by its ability, more or less large, to attenuate the propagation of compromising emanations which would be emitted by the equipment during its operation.

The objective pursued through the application of this concept is to reinforce protection against electromagnetic compromising emanations by installing the equipment, used for the classified data processing, in adapted zones, i.e. those which offer greatest resistance to electromagnetic emissions.

The zones of the building are given starting from measurements of weakening in open space, and the attenuation caused by the physical structure of the building. As zoning takes into account only the weakening of the electromagnetic radiations during their propagation, it is essential that the problems involved in conduction were dealt with as a preliminary according to the methods developed with paragraph 2.2.

2.4.1. Zoning of the installations

The principal objective of the zoning of the installations is to characterize the weakening which a building presents to the electromagnetic propagation. Measurements, necessary to this effect, are taken in the frequency band going of 10 MHz with 1 GHz.

The difference between the measured attenuation, in several points predetermined inside the building, of a signal of reference and the value which this attenuation would have, the same points, if the signal of reference had been emitted in open space, makes it possible to delimit the various zones.

The site and the number of points of measure to the building with zoner must be selected according to the perimeter of security and the various structures of the building. To increase the credit which one grants to this method, it is desirable to take measurements starting from a great number of points. Knowing that the objective of zoning is to measure lowest resistance to the electromagnetic propagation, the sites chosen for the points of measurements retained will have to take account of the type and the thickness of materials used in the construction of the building as well as position of its openings.

In short, the choice of the points of measurements to carry out the zoning of a building, requires the application of some guiding principles of electromagnetism associated with common sense, by taking account of the position of the points of measurements according to the distance between the building and the perimeter of security.

2.4.2. Measure weakening of the buildings

To take this measurement, it is necessary to have an emission unit made up of generators of signals and amplifiers as well as whole of reception made up of an analyzer of spectrum or a field intensity measuring device, associated with a calculator.

For conveniences of the course of measurement, the range of frequencies 10 MHz - 1 GHz can be cut out in several bands. To ensure a good cover of the range of frequencies 10 MHz - 1 GHz, the centre frequency and the width of the sweeping of the generator of signals, in each frequency band, must be selected in such way that the bands overlap.

The level of reference (ref.) of all measurements is given in open space, antennas emission and reception placed at 1 m above the ground and 20 m from one to the other. The signal emission is adjusted on a level not involving saturation of the materials of reception. The generator of signals must be implemented for one duration of sweeping about a few seconds by frequency band whereas receiving side the analysis is regulated for one duration of a few milliseconds.

The antenna emission is placed inside the building, at various predetermined points. The antenna reception is placed in physical limit of protection of the site compared to the emission. The length of the cables and the adjustment of profit must remain identical during all the course of measurements.

2.4.3. Interpretation of results

The interpretation of results consists in comparing, point by point, the levels of references corresponding to the wave propagation in open space, and the levels measured corresponding to the weakening caused by the building. This comparison makes it possible to obtain the attenuation caused by the structure of the building.

The values of the attenuation caused by the structure of the building, compared with predetermined criteria, make it possible to allot a number to the various measured buildings. With the exit of the interpretation of the results of measurements, one can delimit in the field of the building various zones, each one being consisted the whole of the buildings holding an identical number.

The attribution of a number at a zone imposes that 90% at least number of points of measurements must satisfy the requirements of the corresponding criterion.

The value of the measured attenuation (ATM), is compared with the level of reference (ref.), and makes it possible to allot a number to the zone considered according to the criteria below:

Zone 1: ATM (dB) < ref. (dB)

Zone 2: Ref. (dB) < ATM (dB) < ref. (dB) + 20 dB

Zone 3: Ref. (dB) + 20 dB < ATM (dB) < ref. (dB) + 40 dB

Zone 4: Ref. (dB) + 40 dB < ATM (dB)

Formula of the real attenuation:

Vref (dB/*V) - Vatt (dB/*V) = ATM (dB)
Vref = Tension of the signal of reference
Vatt = Tension of the signal measured in the building

An example illustrating the course of the zoning of a standard building appears as Annex 3.

2.4.4. Example of procedure

At the interior of the building - Not emission

1 generator of sinusoidal signals (1 MHz with 1 GHz)

1 set of amplifiers covering the air frequency band

1 set of the air suitable ones at the outside of the building - Not reception (located in limit of zone of safety).

1 analyzer of spectrum

1 preamplifier (in option) or 1 suitable receiver and 1 microcomputer

1 plotting table

1 printer

1 set of air suitable


3.1. Certification of installations:

The certification of the installations of a building, located on the site of the equipment processing classified information, takes place through the preparation of a document articulated in three parts;

- a descriptive file;
- a file of measurements;
- a file of synthesis.
3.1.1. Descriptive file:

The descriptive file must be as complete as possible. It will comprise the overall plan of the site, the plan of the building concerned, as well as the nature and the characteristics of the equipment processing classified information. Overall plan of the site:

The overall plan of the site will specify:

- the position and the nature of the perimeter;
- the position of the building concerned;
- the position and distances from the other buildings to the building concerned;
- the position of the buildings located outside the site near the perimeter;
- various conduits leading to the building:
- energy sources (cables, transformer, etc...);
- sewer, water pipelines, gas, etc...;
- the ground well. Plan of the building:

The interior plan of the building will reveal:

- the location of parts and their use;
- the nature of building materials;
- the route of cables used for:
- power supply;
- telephone service;
- remote control signals of alarm (fire, anti-intrusion...);

- drains which may be unintentional conductors:

- plumbing;
- ventilation;
- central heating;

- the grounded circuit;
- location of Faradized buildings if there are any;
- the map of the buildings if the building were zoned;

- all information considered to be useful. Nature and characteristic of the equipment processing classified information:

A statement on the nature and the characteristics of the equipment will reveal:

- the inventory of the electric and electronic materials used in the building;
- their location;
- description for each equipment and its principal characteristics:
- mark;
- type;
- function;
- energy, consumption;
- connections with outside;
- nature of its cables;

- a diagram of the connections between apparatuses (drawn to scale).

For the equipment processing classified information, the diagram will specify:

- path of information;
- type of signals;
- nature of the cables;
- shielding;
- filters;
- grounding.
3.1.2. File of measurements

This file must gather all the results of the measurements taken in the building and information concerning the zoning of the installations or measurements of weakening of the Faradized buildings.

The analysis of the file of measurements aims at releasing a list of particular points, starting from the requirements of this recommendation defining the criteria of installation per type (distances, filtering, shielding, crossing of cables, etc...).

A visit on the spot will make it possible to count all the disputed or delicate points. With this intention one will examine, for all the parts, the plan of the installations, and one will trace around the materials and of the cables for the zones of coupling.

If it were not possible to put the installations in conformity, with the rules developed in the present recommendation, it will be necessary to take complementary measures to define the real risks of radiation or coupling in order to draw the measures to be taken from them (restriction of employment, particular monitoring, etc...).

3.1.3. File of synthesis:

The file of synthesis will specify:

- the points which are not in conformity with the recommendation, and this due to the requirements of the installations;
- complementary measures to take during the use of certain equipment:
- physical monitoring;
- extension of the zones of secuirty or coupling;
- apparatuses to keep out of service during operation of some others;
- to trace around the equipment and cables zones of radiations;
- to specify the distances, filterings, shieldings, the crossings of cables.

3.2. Maintenance of the installations

Any noted modification, during the check of operations, involves an action of maintenance intended to restore the initial electromagnetic quality of the zone in order to ensure the security of processed data.

The maintenance of the zone consists in making provisions to make it possible to reach, in the field of the electromagnetic propagation on the one hand, and in the field of conduction, on the other hand, the characteristics described in chapter 2. This objective can be achieved using following measurements:

- replacement or modification of the elements charged to treat conduction (adequate filters for the various cables connected to the materials, insulating sleeves for the drains crossing the limit of the zone, etc...);
- displacement of the materials used;
- modification of the perimeter of the zone.

Sometimes it is not the electromagnetic quality of the zone should be blamed but instead the material used. In this case proper maintenance will result in the replacement of the suspect material.

3.3. Control installations

The check of operations consists of ensuring the conformance of current installations with those described in the document prepared for certfication. The essential element of this objective can be attained by a detailed visual examination of the site, and is intended to prevent any modification of the installations (modification of the infrastructure, replacement of the materials, addition of materials, presence of recently approved conductors, etc...).

It is recommended that these checks of operations, to be carried out under the responsibility of the agent in charge of security for the site, proceed this way:

- periodical, once per annum;
- systematic, at the time of any new installation of material or with each modification of the installations.

Along with these controls, detailed attention must be paid to the installation of materials and equipment which do not process classified data but which could collect by induction and retransmit by conduction compromising emanations outside the zones concerned.

The person in charge of security of the site will check periodically that the installation remains in conformity with its initial state.

He will check on the one hand, the validity of the diagrams of establishment of material and on the other hand, that any replacement or new establishment of equipment, is done according to the principles associated with the concept of zoning of the buildings. He will make sure, moreover, that any modification of the infrastructure of the building, any replacement or relocation of conducting cables, conduits and other elements, comply with the rules of this recommendation and do not violate the zoning of the building.


List of national standards

- Standard NF C 15 106 Practical guide: selection of conductors of protection, ground conductors and conductors of equipotential connections;

- Standard NF C 17 100 Rules of lightning protection, installation of lightning conductor.

- Standard NF C 98 020 Electromagnetic compatibility - telephone materials and equipment connected to the public telecommunications network.

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