SIST EN 300 132-2 V2.1.2:2006
(Main)Environmental Engineering (EE); Power supply interface at the input to telecommunications equipment; Part 2: Operated by direct current (dc)
- Abstract
The present document contains requirements for:
- the output performance of the direct current (dc) power equipment at the interface "A";
- the input of the telecommunications equipment connected to interface "A" powered by dc.
The dc voltage at interface "A" may be derived from the AC primary supply. The dc supply may incorporate a backup battery. If any other equipment e.g. datacom equipment, are connected to interface "A" in parallel to telecommunications equipment, all requirements addressed in clause 4 of the present document must be fulfilled. The present document aims at providing compatibility between the power supply equipment and the power consuming telecommunications equipment, and also between different system blocks connected to the same power supply.
NOTE 1: The present document is applicable only to -48 V dc power supply interfaces. However, during a transitional period, other dc voltages may be used in existing installations. Annex A gives guidance on working in conjunction with existing -60 V dc supply systems.
The power supply interface, interface "A", is a physical point to which all the requirements are related (see figure 1).
This point is situated between the power supply system(s) and the power consuming telecommunications equipment.
NOTE 2: Interface "A" is located at the power terminals of the telecommunications equipment. Subject to the installation preconditions this point may be located at any other point between the power supply system and the telecommunications equipment by mutual agreement of the relevant parties.
The requirements at interface "A" apply to:
- the output of the power supply equipment or power supply installation of telecommunications centres;
- the power supply input of telecommunications equipment installed at telecommunication centres;
- telecommunications equipment, installed in customers' premises, whose dc interface "A" is also used by equipment requiring a supply to this specification.
NOTE 3: Normally there is more than one load unit connected to interface "A". In these cases, interface "A" will undergo further restrictions with respect to noise limits or other disturbances specified in clause 4.8.
NOTE 4: Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered within the present document.
NOTE 5: An example of a configuration in which interface "A" is identified is given in annex D.
- Status
- Published
- Publication Date
- 31-Jan-2006
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Feb-2006
- Due Date
- 01-Feb-2006
- Completion Date
- 01-Feb-2006
SIST EN 300 132-2 V2.1.2:2006 is the Slovenian adoption of ETSI EN 300 132-2 V2.1.2, a European telecommunications standard from ETSI. It specifies the direct current (dc) power supply interface at the input to telecommunications equipment, mainly for -48 V systems, so that the power source, protection devices and connected equipment can operate together at the same interface "A". It is used by telecom power-supply designers, equipment manufacturers, operators and test labs that need a common basis for compatibility and testing.
What does SIST EN 300 132-2 V2.1.2:2006 specify?
SIST EN 300 132-2 V2.1.2:2006 specifies the output performance of the dc power equipment at interface "A" and the dc input conditions for telecommunications equipment connected to that interface. It is written to maintain compatibility between the power supply equipment and the power-consuming telecommunications equipment, and also between different system blocks connected to the same supply.
The standard applies to dc power at interface "A" that may be derived from AC primary supply and may include a backup battery. It is stated as applicable only to -48 V dc power supply interfaces, while Annex A gives guidance for working with existing -60 V systems during a transitional period. Where other equipment, such as datacom equipment, is connected in parallel to telecommunications equipment, the requirements in clause 4 apply to the shared interface.
The document is organized into clauses 1 to 7 and informative annexes A to E.
| Annex | What it covers |
|---|---|
| Annex A | Guidance for existing -60 V systems |
| Annex B | Measuring inrush current and transferring recorded pulses to the limit chart |
| Annex C | Test arrangements for injecting electrical noise at interface "A" |
| Annex D | Identification of interface "A" |
| Annex E | Bibliography |
Clause 5 points to EN 300 253 for earthing and bonding. Clauses 6 and 7 state that electrical safety and EMC requirements are covered by relevant external standards.
What are the key requirements of SIST EN 300 132-2 V2.1.2:2006?
SIST EN 300 132-2 V2.1.2:2006 sets the voltage, current, noise and test conditions that equipment at interface "A" must tolerate or generate. In practice, it tells designers what a supply must deliver, what a load must accept, and how to verify both sides with repeatable tests.
Voltage levels and service behavior
Clause 4.1 sets the nominal voltage at -48 V, with the positive conductor connected to earth. Clause 4.2 defines the normal service voltage range for that nominal supply, and the note explains that slight service degradation may be accepted near the lower end of that range.
Clause 4.3 requires equipment to survive abnormal steady-state voltages without damage, including low-voltage and over-voltage conditions. After a return to the normal range, the equipment is expected to recover automatically and resume service without manual intervention or unintended disconnection by fuses, breakers or similar protection devices.
Response to supply transients and voltage changes
Clause 4.3.3 covers voltage transients caused by faults in the distribution system. Telecom equipment operated at nominal -48 V must not be damaged by these transients, and clause 4.3.4 requires continued function within specification after the event.
Clause 4.4 addresses voltage changes caused by regulation of the power supply, such as end cell switching. The test uses a controlled transition at interface "A", and the equipment must keep operating to specification with no data loss or false alarm. For a buyer or integrator, this means the load must tolerate normal supply regulation without triggering service faults.
Protection and current drain
Clause 4.5 requires the supply at interface "A" to be protected by circuit breakers, fuses or similar devices, and it notes that inrush energy must be considered when designing the supply system. Clause 4.6 limits the maximum current drain after abnormal service: for voltages in the normal and abnormal ranges lasting longer than 1 second, the draw must stay within the stated multiple of the nominal current. This matters because the protection device has to remain stable during recovery and battery discharge conditions.
Clause 4.7 sets the inrush current limit at connection of interface "A" and defines how to compare the instantaneous surge current with the maximum continuous input current. Annex B explains how to measure the pulse and map it onto the limit chart. In practice, this is the part that helps engineers choose fuses and breakers that will not trip during power-up.
Conducted immunity and emissions at interface "A"
Clause 4.8 gives conducted immunity requirements for the telecommunications equipment at interface "A". It separates narrowband noise and wideband noise, and the notes tie the wideband requirements to measurement with a psophometer for telephone-type circuits. The clause also limits the injected noise current during compliance checking.
Clause 4.9 sets conducted emissions limits for noise re-injected into the power supply system by the equipment. It again distinguishes narrowband and wideband noise and defines the measurement setup under nominal voltage and rated load. For practical verification, this is the section used to confirm that one unit does not disturb other loads on the same dc bus.
What terms does SIST EN 300 132-2 V2.1.2:2006 define?
- Interface "A" - The terminals where the power supply connects to the system block, and the reference point for all power-interface requirements.
- System block - A functional group of equipment that depends on the same power supply for operation and performance.
- Load unit - Power-consuming equipment that is part of a system block.
- Normal service voltage range - The steady-state voltage range over which the equipment maintains normal service.
- Abnormal voltage range - The steady-state voltage range in which normal service is not expected, but the equipment must survive undamaged.
- Maximum continuous input current - The manufacturer-stated continuous input current for a fully equipped unit at nominal voltage.
- LISN - Line Impedance Stabilization Network, the network used in the measurement setups to simulate supply impedance.
- EUT - Equipment Under Test, the unit being checked against the stated requirements.
Who uses SIST EN 300 132-2 V2.1.2:2006?
SIST EN 300 132-2 V2.1.2:2006 is used by telecommunications equipment manufacturers, dc power-supply designers, network operators, test laboratories and quality or compliance teams. It is also relevant to installers and system integrators who connect several load units to the same interface "A".
Typical uses include defining supply output characteristics, designing equipment input stages, selecting protection devices, planning shared dc distribution, checking inrush current, and verifying conducted immunity and emissions. In customer-premises installations, it helps when the same dc interface is shared by telecommunications equipment and other equipment that must meet the same supply specification.
What changed in SIST EN 300 132-2 V2.1.2:2006 from the previous edition?
The publication history shows an original ETS 300 132-2 edition from 1996, a corrigendum in 1996, ETSI EN 300 132-2 V2.1.1 in January 2003, and EN 300 132-2 V2.1.2 in September 2003. SIST EN 300 132-2 V2.1.2:2006 is the Slovenian standard identical to EN 300 132-2 Version 2.1.2.
Which standards are used with SIST EN 300 132-2 V2.1.2:2006?
| Reference | Contribution |
|---|---|
| IEC 60269-1 | Defines low-voltage fuses used when considering supply protection and inrush behavior |
| EN 60934 | Covers circuit-breakers for equipment, also relevant to supply protection |
| ETSI EN 300 253 | Covers earthing and bonding of telecommunication equipment in telecommunication centres |
| ITU-T Q.551, Q.552, Q.553, Q.554 | Provide transmission characteristics for digital exchanges and analogue interfaces used in the noise context |
| ITU-T O.41 | Defines the psophometer used in wideband noise measurements |
| ETSI TR 100 283 | Gives guidance on transient voltages at interface "A" |
| Part 1 of EN 300 132 | Covers interface operated by alternating current derived from direct current sources |
| Part 3 of EN 300 132 | Covers interface operated by rectified current source, alternating current source or dc source up to 400 V |
What does the SIST EN 300 132-2 V2.1.2:2006 document contain?
The standard contains voltage ranges, protection expectations, inrush-current limits, and conducted immunity and emissions requirements for dc-powered telecommunications equipment. It includes figures for the interface, inrush-current limits, and test circuits, plus tables that define measurement bandwidths for narrowband noise.
Annex B gives a practical method for measuring inrush current and converting recorded pulses onto the limit chart. Annex C shows example arrangements for injecting electrical noise at interface "A", and Annex D shows how interface "A" is identified in typical system layouts.
The document is therefore both a specification and a test guide. Engineers use it to design the supply interface, laboratories use it to set up measurements, and operators use it to check that connected equipment can share the same dc distribution without unwanted disturbance.
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Frequently Asked Questions
SIST EN 300 132-2 V2.1.2:2006 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Environmental Engineering (EE); Power supply interface at the input to telecommunications equipment; Part 2: Operated by direct current (dc)". This standard covers: The present document contains requirements for: - the output performance of the direct current (dc) power equipment at the interface "A"; - the input of the telecommunications equipment connected to interface "A" powered by dc. The dc voltage at interface "A" may be derived from the AC primary supply. The dc supply may incorporate a backup battery. If any other equipment e.g. datacom equipment, are connected to interface "A" in parallel to telecommunications equipment, all requirements addressed in clause 4 of the present document must be fulfilled. The present document aims at providing compatibility between the power supply equipment and the power consuming telecommunications equipment, and also between different system blocks connected to the same power supply. NOTE 1: The present document is applicable only to -48 V dc power supply interfaces. However, during a transitional period, other dc voltages may be used in existing installations. Annex A gives guidance on working in conjunction with existing -60 V dc supply systems. The power supply interface, interface "A", is a physical point to which all the requirements are related (see figure 1). This point is situated between the power supply system(s) and the power consuming telecommunications equipment. NOTE 2: Interface "A" is located at the power terminals of the telecommunications equipment. Subject to the installation preconditions this point may be located at any other point between the power supply system and the telecommunications equipment by mutual agreement of the relevant parties. The requirements at interface "A" apply to: - the output of the power supply equipment or power supply installation of telecommunications centres; - the power supply input of telecommunications equipment installed at telecommunication centres; - telecommunications equipment, installed in customers' premises, whose dc interface "A" is also used by equipment requiring a supply to this specification. NOTE 3: Normally there is more than one load unit connected to interface "A". In these cases, interface "A" will undergo further restrictions with respect to noise limits or other disturbances specified in clause 4.8. NOTE 4: Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered within the present document. NOTE 5: An example of a configuration in which interface "A" is identified is given in annex D.
The present document contains requirements for: - the output performance of the direct current (dc) power equipment at the interface "A"; - the input of the telecommunications equipment connected to interface "A" powered by dc. The dc voltage at interface "A" may be derived from the AC primary supply. The dc supply may incorporate a backup battery. If any other equipment e.g. datacom equipment, are connected to interface "A" in parallel to telecommunications equipment, all requirements addressed in clause 4 of the present document must be fulfilled. The present document aims at providing compatibility between the power supply equipment and the power consuming telecommunications equipment, and also between different system blocks connected to the same power supply. NOTE 1: The present document is applicable only to -48 V dc power supply interfaces. However, during a transitional period, other dc voltages may be used in existing installations. Annex A gives guidance on working in conjunction with existing -60 V dc supply systems. The power supply interface, interface "A", is a physical point to which all the requirements are related (see figure 1). This point is situated between the power supply system(s) and the power consuming telecommunications equipment. NOTE 2: Interface "A" is located at the power terminals of the telecommunications equipment. Subject to the installation preconditions this point may be located at any other point between the power supply system and the telecommunications equipment by mutual agreement of the relevant parties. The requirements at interface "A" apply to: - the output of the power supply equipment or power supply installation of telecommunications centres; - the power supply input of telecommunications equipment installed at telecommunication centres; - telecommunications equipment, installed in customers' premises, whose dc interface "A" is also used by equipment requiring a supply to this specification. NOTE 3: Normally there is more than one load unit connected to interface "A". In these cases, interface "A" will undergo further restrictions with respect to noise limits or other disturbances specified in clause 4.8. NOTE 4: Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered within the present document. NOTE 5: An example of a configuration in which interface "A" is identified is given in annex D.
SIST EN 300 132-2 V2.1.2:2006 is classified under the following ICS (International Classification for Standards) categories: 19.040 - Environmental testing; 33.050.01 - Telecommunication terminal equipment in general. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 300 132-2 V2.1.2:2006 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2006
Okoljski inženiring (EE) – Napajalni vmesnik na vhodu v telekomunikacijsko
opremo – 2. del: Obratovanje z enosmerno napetostjo (dc)
Environmental Engineering (EE); Power supply interface at the input to
telecommunications equipment; Part 2: Operated by direct current (dc)
Ta slovenski standard je istoveten z: EN 300 132-2 Version 2.1.2
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
33.050.01 Telekomunikacijska Telecommunication terminal
terminalska oprema na equipment in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
European Standard (Telecommunications series)
Environmental Engineering (EE);
Power supply interface at the input to
telecommunications equipment;
Part 2: Operated by direct current (dc)
2 ETSI EN 300 132-2 V2.1.2 (2003-09)
Reference
REN/EE-02008[2]
Keywords
Interface, power supply
ETSI
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ETSI
3 ETSI EN 300 132-2 V2.1.2 (2003-09)
Contents
Intellectual Property Rights.4
Foreword.4
1 Scope .5
2 References.6
3 Definitions, symbols and abbreviations .7
3.1 Definitions.7
3.2 Symbols.7
3.3 Abbreviations.8
4 Requirements.8
4.1 Nominal voltage.8
4.2 Normal service voltage range at interface "A" .8
4.3 Abnormal service voltage range at interface "A" .8
4.3.1 Abnormal service voltage under steady-state conditions.8
4.3.2 Recovery from steady state abnormal voltage .8
4.3.3 Voltage transients.9
4.3.4 Recovery from voltage transients .9
4.4 Voltage changes due to the regulation of the power supply.9
4.4.1 Test conditions.9
4.4.2 Performance criteria.9
4.5 Supply protection at interface "A".10
4.6 Maximum current drain following abnormal service .10
4.7 Surge current on connection of interface "A".10
4.7.1 Limits.10
4.7.2 Measurements.11
4.8 Conducted immunity requirements of the telecommunications equipment at interface "A".11
4.8.1 Immunity to narrowband noise .12
4.8.2 Immunity to wideband noise.13
4.9 Conducted emissions requirements of the telecommunications equipment at interface "A".14
4.9.1 Emissions of narrow-band noise.14
4.9.2 Emission of wideband noise .15
5 Earthing and bonding .15
6 Electrical safety requirements .16
7 EMC requirements.16
Annex A (informative): -60 V systems.17
dc
Annex B (informative): Guide for measuring inrush current and for transferring the
recorded pulses onto the limit chart.18
B.1 Measurement.18
B.2 Pulse waveform transformation.19
Annex C (informative): Test arrangements for the injection of electrical noise at interface
"A".20
Annex D (informative): Identification of interface "A".21
Annex E (informative): Bibliography.22
History .23
ETSI
4 ETSI EN 300 132-2 V2.1.2 (2003-09)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Environmental
Engineering (EE).
The present document concerns the requirements for the interface between telecommunications equipment and its
power supply, and includes requirements relating to its stability and measurement. Various other references and detailed
measurement and test arrangements are contained in informative annexes.
The present document is part 2 of a multi-part deliverable covering Environmental Engineering (EE); Power supply
interface at the input to telecommunications equipment, as identified below:
Part 1: "Operated by alternating current (ac) derived from direct current (dc) sources";
Part 2: "Operated by direct current (dc)";
Part 3: "Operated by rectified current source, alternating current source or direct current source up to 400 V".
National transposition dates
Date of latest announcement of this EN (doa): 31 December 2003
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 June 2004
Date of withdrawal of any conflicting National Standard (dow): 30 June 2004
ETSI
5 ETSI EN 300 132-2 V2.1.2 (2003-09)
1 Scope
The present document contains requirements for:
- the output performance of the direct current (dc) power equipment at the interface "A";
- the input of the telecommunications equipment connected to interface "A" powered by dc.
The dc voltage at interface "A" may be derived from the AC primary supply. The dc supply may incorporate a backup
battery.
If any other equipment e.g. datacom equipment, are connected to interface "A" in parallel to telecommunications
equipment, all requirements addressed in clause 4 of the present document must be fulfilled.
The present document aims at providing compatibility between the power supply equipment and the power consuming
telecommunications equipment, and also between different system blocks connected to the same power supply.
NOTE 1: The present document is applicable only to -48 V power supply interfaces. However, during a
dc
transitional period, other dc voltages may be used in existing installations. Annex A gives guidance on
working in conjunction with existing -60 V supply systems.
dc
The power supply interface, interface "A", is a physical point to which all the requirements are related (see figure 1).
This point is situated between the power supply system(s) and the power consuming telecommunications equipment.
NOTE 2: Interface "A" is located at the power terminals of the telecommunications equipment. Subject to the
installation preconditions this point may be located at any other point between the power supply system
and the telecommunications equipment by mutual agreement of the relevant parties.
The requirements at interface "A" apply to:
- the output of the power supply equipment or power supply installation of telecommunications centres;
- the power supply input of telecommunications equipment installed at telecommunication centres;
- telecommunications equipment, installed in customers' premises, whose dc interface "A" is also used by
equipment requiring a supply to this specification.
NOTE 3: Normally there is more than one load unit connected to interface "A". In these cases, interface "A" will
undergo further restrictions with respect to noise limits or other disturbances specified in clause 4.8.
NOTE 4: Disturbances on the power supply interface "A" relating to the continuous wave phenomena below
20 kHz are covered within the present document.
NOTE 5: An example of a configuration in which interface "A" is identified is given in annex D.
ETSI
6 ETSI EN 300 132-2 V2.1.2 (2003-09)
telecommunications
equipment
DC power supply conductors
System block
Interface "A"
Figure 1: Identification of interface "A"
The purpose of the present document is:
- to use a power supply system with the same characteristics for all telecommunications equipment defined in
the area of application;
- to facilitate inter working of different (types of) load units;
- to facilitate the standardization of telecommunications equipment;
- to facilitate the installation, operation and maintenance in the same network of equipment and
telecommunications systems from different origins.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
[1] IEC 60269-1: "Low-voltage fuses - Part 1: General requirements".
[2] EN 60934: "Circuit-breakers for equipment (CBE)".
[3] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of telecommunication
equipment in telecommunication centres".
[4] ITU-T Recommendation Q.551: "Transmission characteristics of digital exchanges".
[5] ITU-T Recommendation Q.552: "Transmission characteristics at 2-wire analogue interfaces of
digital exchanges".
[6] ITU-T Recommendation Q.553: "Transmission characteristics at 4-wire analogue interfaces of
digital exchanges".
ETSI
7 ETSI EN 300 132-2 V2.1.2 (2003-09)
[7] ITU-T Recommendation Q.554: "Transmission characteristics at digital interfaces of digital
exchanges".
[8] ITU-T Recommendation O.41: "Psophometer for use on telephone-type circuits".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
abnormal voltage range: range of steady-state voltage over which the equipment will not be expected to maintain
normal service but will survive undamaged
customer premises: any location which is the sole responsibility of the customer
interface "A": terminals at which the power supply is connected to the system block
NOTE 1: See also figure 1.
NOTE 2: This is a functional definition and not an exact depiction of the physical location.
load unit: power-consuming equipment, that is part of a system block
maximum continuous input current: maximum continuous input current, stated by the manufacturer, for a
fully-equipped equipment under test connected to interface "A", at nominal voltage (accordance clause 4.7.1 of
EN 300 132-2)
normal service: service mode where telecommunications equipment operates within its specification
normal service voltage range: range of steady-state voltages over which the equipment will maintain normal service
nominal voltage: nominal value of the voltage that designates the type of supply
power supply: power source to which telecommunications equipment is intended to be connected
system block: functional group of equipment depending for its operation and performance on its connection to the same
power supply
NOTE: A system block may consist of equipment or a functional group of equipment. Different examples of
configurations at interface "A" are given in annex D.
telecommunication centre: location where telecommunications equipment is installed and which is the sole
responsibility of the operator
3.2 Symbols
For the purposes of the present document, the following symbols apply:
I instantaneous surge current (see clause 4.7.1)
t
I maximum continuous input current
m
L inductance of inductive element of LISN
R resistance of resistive element of LISN
t time
Z capacitive impedance of immunity measurement circuit
c
Z resistive impedance of immunity measurement circuit
m
ETSI
8 ETSI EN 300 132-2 V2.1.2 (2003-09)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
dc direct current (also when used as a suffix to units of measurement)
EUT Equipment Under Test
LISN Line Impedance Stabilization Network
rms root mean square (also when used as a suffix to units of measurement)
4 Requirements
4.1 Nominal voltage
The nominal value of the voltage at interface "A" shall be -48 V (positive conductor is connected to earth).
dc
NOTE 1: In most cases the voltage of interface "A" will be complemented by a 24 cell lead-acid battery.
NOTE 2: During a transitional period, other dc voltages may be used in existing installations. Annex A gives
guidance on merging equipment with existing -60 V supply systems.
dc
4.2 Normal service voltage range at interface "A"
The normal service voltage range for the -48 V nominal supply at interface "A" shall be -40,5 V to -57,0 V .
dc dc dc
NOTE 1: The minimum voltage is based on the voltage drop in the distribution network and a battery cell end of
discharge voltage.
NOTE 2: The voltages specified are measured at interface "A". It should be noted that if interface "A" is at any
point other than the telecommunications equipment interface there will be a voltage drop between
interface "A" and the equipment terminals.
NOTE 3: When the voltage is in the range -40,5 V to -44,0 V it is recognized that there may be a slight
dc dc
degradation of service performance.
4.3 Abnormal service voltage range at interface "A"
4.3.1 Abnormal service voltage under steady-state conditions
Telecommunications equipment operated at -48 V shall not suffer any damage when subjected to the following
dc
voltage ranges:
0,0 V to -40,5 V and
dc dc
-57,0 V to -60,0 V
dc dc
4.3.2 Recovery from steady state abnormal voltage
Following the restoration of the supply to the normal voltage range, the power conversion and management systems on
the l
...