EN 60027-2:2007

SLOVENSKI STANDARD
01-januar-2008
1DGRPHãþD
SIST HD 60027-2:2004
ýUNRYQLVLPEROL]DXSRUDERYHOHNWURWHKQRORJLMLGHO7HOHNRPXQLNDFLMHLQ
HOHNWURQLND,(&
Letter symbols to be used in electrical technology -- Part 2: Telecommunications and
electronics
Formelzeichen für die Elektrotechnik - Teil 2: Telekommunikation und Elektronik
Symboles littéraux à utiliser en électrotechnique -- Partie 2: Télécommunications et
électronique
Ta slovenski standard je istoveten z: EN 60027-2:2007
ICS:
01.075 Simboli za znake Character symbols
31.020 Elektronske komponente na Electronic components in
splošno general
33.020 Telekomunikacije na splošno Telecommunications in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 60027-2
NORME EUROPÉENNE
April 2007
EUROPÄISCHE NORM
ICS 01.060 Supersedes HD 60027-2:2003

English version
Letter symbols to be used in electrical technology -
Part 2: Telecommunications and electronics
(IEC 60027-2:2005)
Symboles littéraux à utiliser  Formelzeichen
en électrotechnique - für die Elektrotechnik -
Partie 2: Télécommunications Teil 2: Telekommunikation
et électronique und Elektronik
(IEC 60027-2:2005)
(CEI 60027-2:2005)
This European Standard was approved by CENELEC on 2007-04-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60027-2:2007 E
Foreword
The text of the International Standard IEC 60027-2:2005, prepared by IEC TC 25, Quantities and units,
and their letter symbols, was submitted to the Unique Acceptance Procedure and was approved by
CENELEC as EN 60027-2 on 2007-04-01 without any modification.
This European Standard supersedes HD 60027-2:2003.
– it contains a revision of some clauses of HD 245.2 S1:1983 that were not technically revised in
HD 60027-2:2003;
– it contains a revision of Clause 8 which is now Clause 10;
– it contains some new clauses dealing with subjects that were not previously considered;
– former Clause 10 will be given in another part of EN 60027;
– former Clause 11 will be revised as EN 60027-6.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2008-04-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2010-04-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60027-2:2005 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 60027-2:2007
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

1)
IEC 60027-1 1992 Letter symbols to be used in electrical EN 60027-1 2006
technology -
Part 1: General
IEC 60027-3 2002 Letter symbols to be used in electrical EN 60027-3 2007
technology -
Part 3: Logarithmic and related quantities,
and their units
IEC 60050-101 1998 International Electrotechnical Vocabulary - -
(IEV) -
Part 101: Mathematics
IEC 60050-131 2002 International Electrotechnical Vocabulary - - -
Part 131: Circuit theory
IEC 60050-191 1990 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 191: Dependability and quality of
service
IEC 60050-351 1998 International Electrotechnical Vocabulary - -
(IEV) -
Part 351: Automatic control
IEC 60050-702 1992 International electrotechnical vocabulary - -
(IEV) -
Chapter 702: Oscillations, signals and related
devices
IEC 60050-704 1993 International electrotechnical vocabulary - -
(IEV) -
Chapter 704: Transmission
IEC 60050-705 1995 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 705: Radio wave propagation

IEC 60050-712 1992 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 712: Antennas
1)
EN 60027-1 is based on IEC 60027-1:1995 (Reprint) + A1:1997.

Publication Year Title EN/HD Year
IEC 60050-713 1998 International Electrotechnical Vocabulary - -
(IEV) -
Part 713: Radiocommunications: transmitters,
receivers, networks and operation

IEC 60050-715 1996 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 715: Telecommunication networks,
teletraffic and operation
IEC 60050-721 1991 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 721: Telegraphy facsimile and data
communication
IEC 60050-722 1992 International electrotechnical vocabulary - -
(IEV) -
Chapter 722: Telephony
IEC 60050-723 1997 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 723: Broadcasting: Sound, television
and data
IEC 60050-725 1994 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 725: Space radiocommunications

IEC 60050-726 1982 International electrotechnical vocabulary - -
(IEV) -
Part 726: Transmission lines and waveguides

IEC 60050-731 1991 International Electrotechnical Vocabulary - -
(IEV) -
Chapter 731: Optical fibre communication

IEC 60122-1 2002 Quartz crystal units of assessed quality - EN 60122-1 2002
Part 1: Generic specification
IEC 60375 2003 Conventions concerning electric and EN 60375 2003
magnetic circuits
IEC 60747 Series Semiconductor devices - -

IEC 60747-1 1983 Semiconductor devices - - -
Part 1: General
IEC 60748 Series Semiconductor devices - - -
Integrated circuits
IEC 60748-1 2002 Semiconductor devices - Integrated circuits - - -
Part 1:General
IEC 61703 2001 Mathematical expressions for reliability, EN 61703 2002
availability, maintainability and maintenance
support terms
IEC/TR 61931 1998 Fibre optic - Terminology - -

ISO/IEC 2382-16 1996 Information technology - Vocabulary - - -
Part 16: Information theory
- 5 - EN 60027-2:2007
Publication Year Title EN/HD Year
ISO 31-0 1992 Quantities and units - - -
Part 0: General principles
ISO 31-11 1992 Quantities and units - - -
Part 11: Mathematical signs and symbols for
use in the physical sciences and technology

NORME CEI
INTERNATIONALE
IEC
60027-2
INTERNATIONAL
Troisième édition
STANDARD
Third edition
2005-08
Symboles littéraux à utiliser en électrotechnique –
Partie 2:
Télécommunications et électronique

Letter symbols to be used in electrical
technology –
Part 2:
Telecommunications and electronics

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Pour prix, voir catalogue en vigueur
For price, see current catalogue

60027-2  IEC:2005 – 3 –
CONTENTS
FOREWORD.5

1 Scope.9
2 Normative references .9
3 General concepts .13
3.1 General .13
3.2 Linear networks.35
3.2.1 General .35
3.2.2 Two-port linear networks under sinusoidal conditions .35
3.2.3 n-port linear networks under sinusoidal conditions .53
3.3 Line transmission of signals and telephony.65
3.3.1 General .65
3.3.2 Line transmission .65
3.3.3 Subscripts for line transmission .67
3.3.4 Telephony .69
3.3.5 Subscripts for telephony .71
3.4 Waveguide propagation.73
3.4.1 Frequency and wavelength in a waveguide.73
3.4.2 Characteristic and normalized impedance and admittance in general
(unbounded space, waveguide or transmission line) .73
3.4.3 Impedance and admittance at a point in a substance.75
3.4.4 Impedance and admittance at a point in vacuum .75
3.4.5 Impedance and admittance of a waveguide .77
3.5 Radiocommunications .79
3.5.1 General .79
3.5.2 General and tropospheric propagation .79
3.5.3 Ionospheric propagation .83
3.5.4 Antennas .85
3.5.5 Radio links .93
3.6 Optical fibre communication .97
3.7 Television.107
3.8 Data processing and data transmission .111
3.8.1 Teletraffic .111
3.8.2 Data processing and digital transmission.113
3.8.3 Prefixes for binary multiples .121
3.9 Information theory .123
3.10 Dependability .129
3.11 Equivalent circuits of piezoelectric crystal units .133
3.12 Semiconductor devices .141
3.13 Electroacoustics .141

60027-2  IEC:2005 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LETTER SYMBOLS TO BE USED IN ELECTRICAL TECHNOLOGY –

Part 2: Telecommunications and electronics

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60027-2 has been prepared by IEC technical committee 25:
Quantities and units, and their letter symbols.
This third edition cancels and replaces the second edition published in 2000. This third edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) it contains a revision of some clauses of the first edition that were not technically revised
in the second edition;
b) it contains a revision of Clause 8 which is now Clause 10;
c) it contains some new clauses dealing with subjects that were not previously considered;
d) former Clause 10 will be given in another part of IEC 60027;
e) former Clause 11 will be revised as IEC 60027-6.

60027-2  IEC:2005 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
25/298/FDIS 25/304/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 60027 consists of the following parts, under the general title Letter symbols to be used in
electrical technology:
Part 1: General
Part 2: Telecommunications and electronics
Part 3: Logarithmic and related quantities, and their units
Part 4: Symbols for quantities to be used for rotating electrical machines
Part 6: Control technology
Part 7: Physiological quantities and units
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date T indicated on the IEC web site under Thttp://webstore.iec.ch T in the
data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60027-2  IEC:2005 – 9 –
LETTER SYMBOLS TO BE USED IN ELECTRICAL TECHNOLOGY –

Part 2: Telecommunications and electronics

1 Scope
This part of IEC 60027 is applicable to telecommunications and electronics. It gives names
and symbols for quantities and units.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60027-1:1992, Letter symbols to be used in electrical technology – Part 1: General
IEC 60027-3:2002, Letter symbols to be used in electrical technology – Part 3: Logarithmic
and related quantities
IEC 60050-101:1998, International Electrotechnical Vocabulary – Part 101: Mathematics
IEC 60050-131:2002, International Electrotechnical Vocabulary – Part 131 – Circuit theory
IEC 60050-191:1990, International Electrotechnical Vocabulary – Part 191: Dependability and
quality of service
IEC 60050-351:1998, International Electrotechnical Vocabulary – Part 351: Automatic control
IEC 60050-702:1992, International Electrotechnical Vocabulary – Part 702: Oscillations,
signals and related devices
IEC 60050-704:1993, International Electrotechnical Vocabulary – Part 704: Transmission
IEC 60050-705:1995, International Electrotechnical Vocabulary – Part 705: Radio wave
propagation
IEC 60050-712:1992, International Electrotechnical Vocabulary – Part 712: Antennas
IEC 60050-713:1998, International Electrotechnical Vocabulary – Part 713: Radiocommuni-
cations: transmitters, receivers, networks and operation
IEC 60050-715:1996, Telecommunication networks, teletraffic and operation
IEC 60050-721:1991, International Electrotechnical Vocabulary – Part 721: Telegraphy,
facsimile and data communication
IEC 60050-722:1992, International Electrotechnical Vocabulary – Part 722: Telephony
IEC 60050-723:1997, International Electrotechnical Vocabulary – Part 723: Broadcasting:
sound, television, data
60027-2  IEC:2005 – 11 –
IEC 60050-725:1994, International Electrotechnical Vocabulary – Part 725: Space radio-
communications
IEC 60050-726:1982, International Electrotechnical Vocabulary – Part 726: Transmission lines
and waveguides
IEC 60050-731:1991, International Electrotechnical Vocabulary – Part 731: Optical fibre
communication
IEC 60122-1:2002, Quartz crystal units of assessed quality – Part 1: Generic specification
IEC 60375:2003, Conventions concerning electric and magnetic circuits
IEC 60747(all parts), Semiconductor devices – Discrete devices
IEC 60747-1:1983, Semiconductor devices – Discrete devices – Part 1: General
IEC 60748 (all parts), Semiconductor devices – Integrated circuits
IEC 60748-1:2002, Semiconductor devices – Integrated circuits – Part 1: General
IEC 61703:2001, Mathematical expressions for reliability, availability, maintainability and
maintenance support terms
IEC 61931:1998, Fibre optic – Terminology
ISO/IEC 2382-16:1996, Information technology – Vocabulary – Part 16: Information theory
ISO 31-0:1992, Reference materials – Contents of certificates and labels
ISO 31-11:1992, Quantities and units – Part 11: Mathematical signs and symbols for use in
the physical sciences and technology
NOTE 1 In this part of IEC 60027, complex quantities are denoted by underlining their symbols. However, this
does not constitute a compulsory rule in applications (see 1.6 in IEC 60027-1).
NOTE 2 The heading in the tables "Unit, coherent with the SI" covers SI units and other units coherent with the
SI, such as bar and neper.
60027-2  IEC:2005                 – 13 –

3 General concepts
3.1 General
For logarithmic quantities defined as a logarithm of the ratio of two power or field quantities, respectively, the neper, Np, is coherent with the SI and is a
special name for the unit one. In practice, however, the submultiple decibel, dB, of the bel, B, is generally used. The bel is not explicitly mentioned in the
table. See IEC 60027-3.
Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
101 101-12-02 signal The value of a signal is proportional to a physical quantity   The unit depends on
S , s
702-04-01 considered as representing information, with an arbitrary
the kind of quantity
(generic term)
351-12-16 constituting the signal
scale. In this document, S and S are used for input and
1 2
(electric current,
output signals respectively; see IEC 60027-1:1992 for
voltage, pressure,
suitable subscripts. In cases where the type of signal
etc.).
quantity is known, for example, electric current, voltage,
pressure, etc., use the appropriate symbol.
With respect to capital and lower-case letters, see
IEC 60027-1:1992, 2.1.
102 signal power "s" (lower case, upright) is used as subscript for "signal". watt W  In a physical system,
P P
s sig
a signal power is
In signal theory, the term "instantaneous power" is by
always a physical
convention used for the square of the instantaneous value
power.
of a signal. This square is proportional to a physical power
if the signal is a field quantity
(see IEV 101-14-71, Note 1).
103 signal level   In practice, a base for
L L , L S
s sig
L = log
the logarithm has to
S
ref
be specified.
where S and S are two signals of the same kind, S
ref ref
being a reference
103.1 702-07-04 absolute power neper Np decibel dB
1 P P
L
P
L = ln Np = 10 lg dB
level; power level
P
2 P P
ref ref
where P is a power and P is a reference power
ref
60027-2  IEC:2005                 – 15 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
103.2 702-07-06 absolute voltage neper Np decibel dB
U U
L
U
L = ln Np = 20 lg dB
level; voltage
U
U U
ref ref
level; absolute
tension level;
where U is a voltage and U is a reference voltage
ref
tension level
103.3 702-07-05 relative power neper Np decibel dB
L = L − L
L
r r,x P,x P,0
level
x refers to the measuring point and 0 to the reference
point
∞
103.4 101-14-71 power spectral watt W/Hz  In a physical system,
w( f )
N is
702-04-50 density per the power spectral
P = w( f )d f
used for
∫
hertz density is always a
(for a signal or
the power
physical power
noise)
spectral where f is frequency.
spectral density.
density of
In signal theory, the term "instantaneous power" is by
a white
convention used for the square of the instantaneous value
noise
of a signal or noise. This square is proportional to a
physical power if the signal or the noise is a field quantity
(see IEV 101-14-71, Note 1).
104 101-14-63 noise Concerning upper-case and lower-case letters, see   The unit depends on
N , n
S , s
n n
702-08-03 IEC 60027-1:1992, 2.1. the kind of quantity
(generic term)
constituting the noise
"n" (lower case, upright) is used as subscript for "noise".
(electric current,
The value of a noise is proportional to a physical quantity
voltage, pressure,
apparently not conveying information, with an arbitrary
etc.).
scale. In cases where the type of noise quantity is known,
use the appropriate symbol (for example, I, i for electric
current) with n as subscript.
105.1 702-08-51 equivalent noise Applies to a one-port network. volt V
U
n
voltage;
equivalent noise
tension
60027-2  IEC:2005                 – 17 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
105.2 702-08-52 equivalent noise Applies to a one-port network. ohm
Ω
R , R
eq n
resistance; noise 2
U
n
resistance R =
eq
4kT Δf
ref
where k is the Boltzmann constant, T is a reference
ref
temperature and Δf is the frequency bandwidth
considered.
106 702-08-54 spot noise Applies to a one-port network. kelvin K
T(f)
temperature
f is frequency
106.1 702-08-55 mean noise Applies to a one-port network. kelvin K
T
temperature
107 702-08-56 equivalent spot Applies to a two-port network. kelvin K
T ( f )
eq
noise
f is frequency
temperature
107.1 702-08-58 mean equivalent Applies to a two-port network. kelvin K
T eq
noise
temperature;
mean noise
temperature
107.2 702-08-57 spot noise factor Applies to a two-port network. one 1
F( f )
The noise factor is the ratio of the exchangeable power
spectral density of output noise to the power spectral
density which would be present at the output if the only
source of noise were input thermal noise at a reference
temperature T :
ref
T ( f )
eq
F( f ) = 1+
T
ref
where f is frequency.
60027-2  IEC:2005                 – 19 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
107.3 spot noise factor neper Np decibel dB
702-08-57
F ( f ) 1
n
F()f = ln F()f Np = 10 lg F( f) dB
n
(Note 2)
where f is frequency.
In English, the term “noise factor” is generally used for the
arithmetic expression and term “noise figure” is used for
the logarithmic expression.
Applies to a two-port network.
107.4 702-08-59 mean noise one 1
F
factor; noise
T
eq
factor
F = 1+
T
ref
where T is a reference temperature.
ref
107.5 702-08-59 mean noise neper Np decibel dB
F
F = ln F Np = 10 lg F dB
figure; noise n
n
(Note 2)
figure
In English, “noise factor" is generally used for the
arithmetic expression and “noise figure” is used for the
logarithmic expression.
∞
108 702-08-60 effective noise hertz Hz
B
n
bandwidth
B = g( f ) d f
n
∫
g
max
Applies to a two-port network where g(f) is the available
power gain factor as a function of frequency f
(see IEV 702-07-12).
109 702-08-61 signal-to-noise Signal power divided by noise power. one 1
k
SN
ratio; SNR
In practice, the symbol S/N is generally used.
(abbreviation)
109.1 signal-to-noise neper Np decibel dB
K
SN
K = ln k Np = 10 lg k dB
logarithmic ratio
SN SN SN
In practice, the symbol S/N is generally used.

60027-2  IEC:2005                 – 21 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
110 702-07-27 transfer function   The unit of the
UH U UT U
S (ω)
H =
351-14-07
quantity H is equal
S (ω)
to the quotient of the
where S and S are the complex representations of the
1 2
unit of S by the unit
signals as functions of the angular frequency ω .
of S .
When the signals are of the same kind, the transfer
function is sometimes called gain factor.
111 transfer exponent one 1  Special units are only
Γ Γ = A + j B
used when the real
If the transfer function H is of dimension one: and imaginary parts
are treated
H = exp()−Γ
separately.
112 logarithmic neper Np decibel dB

A
A = Re (Γ ) Np = 20 (lge) Re (Γ ) dB
attenuation
113 phase change ϕ radian rad degree
°
B π
B = Im (Γ ) rad
1° = rad
114 voltage one 1
a U
U
a =
attenuation
U
U
factor; tension
Subscripts 1 and 2 may for example designate the input
attenuation factor
port and the output port, respectively, of a two-port
network.
114.1 logarithmic neper Np decibel dB
U U
A
U 1 1
A = ln Np = 20 lg dB
voltage U
U U
2 2
attenuation;
Subscripts 1 and 2 may, for example, designate the input
logarithmic
port and the output port, respectively, of a two-port
tension
network.
attenuation
115 voltage gain one 1
U
g
U 2
g =
factor, tension
U
U
gain factor
Subscripts 1 and 2 may, for example, designate the input
port and the output port, respectively, of a two-port
network.
60027-2  IEC:2005                 – 23 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
115.1 logarithmic neper Np decibel dB
U U
G
2 2
U
G = ln Np = 20 lg dB
voltage gain;
U
U U
1 1
logarithmic
tension gain When the logarithmic voltage gain is negative, its absolute
value is the logarithmic voltage attenuation.
one 1
116 702-02-10 power loss factor Use subscript S instead of P in the case of apparent
a
P
powers.
P
a =
P
P
Subscripts 1 and 2 are used to designate the power of a
signal at two points, for example, input and output of a two-
port network, or the power of a signal in two specified
conditions, for example, for defining insertion loss.
116.1 702-02-10 logarithmic power neper Np decibel dB
Use subscript S instead of P in the case of apparent
A
P
loss
powers.
1 P P
1 1
A = ln Np = 10 lg dB
P
2 P P
2 2
When the logarithmic power loss is negative, its absolute
value is the logarithmic power gain.
117 702-02-11 power gain factor one 1
Use subscript S instead of P in the case of apparent
g
P
powers.
P
g =
P
P
Subscripts 1 and 2 are used to designate the power of a
signal at two points, for example, input and output of a two-
port network, or the power of a signal in two specified
conditions, for example, for defining available power gain.

60027-2  IEC:2005                 – 25 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
117.1 702-02-11 logarithmic power neper Np decibel dB
Use subscript S instead of P in the case of apparent
G
P
gain
powers.
1 P P
2 2
G = ln Np = 10 lg dB
P
2 P P
1 1
When the logarithmic power gain is negative, its absolute
value is the logarithmic power loss.
118 702-02-13 propagation metre −1 Special units are only
γ γ = α + j β
m
coefficient to the used when the real
power and imaginary parts
minus are treated
one separately. See 119
and 120.
119 702-02-14 attenuation neper Np/m decibel dB/m
α
α = Re γ
coefficient per per
metre metre
120 702-02-15 phase change radian rad/m degree
°/m
β
β = Re γ
coefficient per per
metre metre
121 702-02-16 phase delay seconds
t τ
ϕ ϕ
122 702-02-20 group delay seconds
t τ
g g
123 702-02-17 phase velocity Phase velocity is defined for waves only. If both waves and metre m/s
c ,v
ϕ ϕ
per
moving particles are involved, use c for the former and v
c, v
second
for the latter.
ω
c = f λ =
ϕ
k
where f is frequency, λ is wavelength, ω is angular
frequency, and k is angular wavenumber.

60027-2  IEC:2005                 – 27 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
124 702-02-17 group velocity Group velocity is defined for waves only. If both waves and metre m/s

c ,v
g g
per
moving particles are involved, use c for the former and
v
second
for the latter.
d f dω
c = =
g
1 d k
d
λ
where f is frequency, λ is wavelength, is angular
ω
frequency, and k is angular wavenumber.
125 702-02-18 wavelength metre m

λ
c
ϕ
λ =
f
126 702-07-24 complex one 1
S
r
r
r =
726-07-08 reflection factor;
S
i
reflection factor
where S and S are the complex amplitudes of the
i r
incident and reflected wave, respectively.
Z − Z
2 1
r =
Z + Z
2 1
where Z is the characteristic impedance of a transmission
line ahead of a discontinuity or the impedance of the
source; and Z is the impedance after the discontinuity or
the load impedance seen from the junction between the
source and the load. The sign is for the reflection factor for
voltage.
127 standing wave s one 1
1+ r
S
max
ratio
s = =
S
1− r
min
60027-2  IEC:2005                 – 29 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
128 726-07-07 complex one 1
S
τ
t
transmission τ =
S
i
factor;
transmission
where S and S are the complex amplitudes of the
i t
factor
incident and transmitted wave, respectively.
129 101-14-37 complex angular second -1 Special units are only
p
s s = σ + jω = −δ + jω
s
frequency to the used when the real
power and imaginary parts
minus are treated
one separately.
σ
130 growth coefficient neper Np/s decibel dB/s
example:
per per
σ t
u()t = uˆ e sinωt
second second
131 damping neper Np/s decibel dB/s
δ = −σ
δ
coefficient per per
second second
132 reference hertz Hz
f f
ref 0
frequency
133  hertz Hz
resonance
f , f
r rsn
frequency
134 cut-off frequency  hertz Hz
f
c
135 702-01-03 frequency hertz Hz

f , B,Δf
B
702-01-04 bandwidth;
bandwidth
136 702-06-19 modulation factor one 1
m s(t) = sˆ(1+ m sinωt)sin Ω t
(in amplitude
where Ω is the angular frequency of the carrier oscillation;
modulation)
ω is the angular frequency of the modulation oscillation.

60027-2  IEC:2005                 – 31 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
137.1 702-04-54 amplitude (of a jϑ(t)  The unit depends on

A(t)
S(t) = A(t)e
signal) the kind of quantity
where S(t) is the analytic signal associated with the given
constituting the signal
or noise (electric
real signal (see IEV 702-04-52).
current, voltage,
pressure, etc.).
137.2 702-04-55 phase (of a jϑ(t) radian rad degree
ϑ(t) ψ (t) °
π
S(t) = A(t)e
1° = rad
signal)
where S(t) is the analytic signal associated with the given
real signal (see IEV 702-04-52).
138 702-06-38 modulation index η radian rad degree
°
δ s(t) = sˆ sin(Ω t + δ sinωt) π
1° = rad
(in frequency
where Ω is the angular frequency of the carrier oscillation;
modulation);
ω is the angular frequency of the modulation oscillation.
frequency
deviation ratio;
deviation ratio
139 702-04-56 instantaneous hertz Hz

f (t) 1 dϑ(t)
f (t) =
frequency
2π dt
140 702-06-33 instantaneous hertz Hz
Δ f (t)
Δ f (t) = (Δ f ) cosωt
mm
frequency
deviation;
frequency
deviation
141 702-06-34 peak frequency hertz Hz
(Δ f ) f (Δf ) =ωδ /2π
mm d mm
deviation; peak
deviation
142 702-06-31 instantaneous radian rad degree
°
π
Δϑ()t Δϑ()t = (Δϑ) sinωt
mm
1° = rad
phase deviation;
phase deviation
143 702-06-32 peak phase radian rad degree
°
π
(Δϑ) ϑ s()t = sˆ sin(Ω t + (Δϑ) sinωt)
mm d mm
1° = rad
deviation; peak
deviation
60027-2  IEC:2005                 – 33 –

Quantities Units
Item Entry Name of Chief Reserve Remarks Unit, coherent Other units Remarks
number number quantity symbol symbol with the SI
in IEV
Name SymbolName Symbol
144 101-14-55 total harmonic one 1
d k
2 2
()U −U
702-04-51 factor; harmonic 1
d =
factor
U
where U is the r.m.s value of a periodic quantity and U is
the r.m.s value of its fundamental component.
The given symbols are also recommended for quantities
characterizing distortion in general without regard to the
cause or the kind of the distortion considered. In special
cases, it shall be mentioned explicitly which kind of
distortion is meant, using the given symbols with suitable
subscripts if necessary. Example: total harmonic distortion
d (or k ), see IEV 702-07-62.
h h
60027-2  IEC:2005 – 35 –
3.2 Linear networks
3.2.1 General
Quantities considered in this clause are generally complex; however, they are not underlined.
For indicating the matrix character of a quantity, bold face italic type for letter symbols is
recommended, for example Z . If such type is not available, parentheses may be placed
around the letter symbol, for example (Z ) (see ISO 31-11, item 11.1).
ij
3.2.2 Two-port linear networks under sinusoidal conditions
For determining signs of matrix elements, the convention indicated in Figure 1 below is used,
as specified in IEC 60375.
I I
1 2
+
+
U
U
I I
1 2
IEC  1266/05
Figure 1 – Conventions concerning signs in electric circuits
For the representation of two-port matrices, capital letter symbols are preferred in the general
case. If a two-port network contains internal two-ports (such as electronic devices),
preference is given to lower-case symbols for the internal two-ports. See also IEC 60747-
1:1983 (chapter V, 3.2).
60027-2  IEC:2005                – 37 –

Quantities Units
Item Entry Name of quantity Chief Reserve Remarks Unit, coherent with Remarks
number number symbol symbol the SI
in IEV
Name Symbol
201 input impedance  Term and symbol for general use. ohm Ω
The symbol for the corresponding admittance has the same subscript.
Z
Z is the input impedance at port 1. Z is the input impedance at port 2.
1 2
When 1 and 2 are not suitable subscripts for input and output, see
IEC 60027-1:1992, Table 6.
202 output impedance Term and symbol for general use. ohm
Ω
Z
The symbol for the corresponding admittance has the same subscript.
Z is the input impedance at port 1. Z is the input impedance at port 2.
1 2
When 1 and 2 are not suitable subscripts for input and output, see
IEC 60027-1:1992, Table 6.
203 characteristic The symbol for the corresponding admittance has the same subscript. ohm Ω
Z , Z Z
0 c ch
impedance
204 image impedance The symbol for the corresponding admittance has the same subscript. ohm
Ω
Z Z
i im
205 iterative impedance The symbol for the corresponding admittance has the same subscript. ohm Ω
Z , Z
k it
206 impedance matrix
z U I
    Z Z 
Z
1 1 11 12
= Z where Z =
     
U I Z Z
2 2 21 22
     
206.1 open-circuit input ohm
Ω
 U 
Z z
11 11
impedance  
I
 1
I =0
Other symbols can be derived by using suitable subscripts for open-circuit
conditions, as given in IEC 60027-1.
206.2 open-circuit input ohm
Ω
U
 
Z z 1
12 12
reverse transfer  
I
 
impedance I =0
206.3 open-circuit input ohm
Ω
 U 
Z z
21 21
forward transfer  
I
 1
impedance; open-
I =0
circuit input transfer
impedance
60027-2  IEC:2005                – 39 –

Quantities Units
Item Entry Name of quantity Chief Reserve Remarks Unit, coherent with Remarks
number number symbol symbol the SI
in IEV
Name Symbol
206.4 open-circuit output ohm
Ω
 U 
Z z
22 22
impedance  
I
 2
I =0
Other symbols can be derived by using suitable subscripts for open-circuit
conditions, as given in IEC 60027-1.
207 admittance matrix
y I U Y Y
     
Y 1 1
11 12
=Y where Y =
     
I U Y Y
2 2 21 22
     
207.1 short-circuit input siemens S
 I 
Y y
11 11
admittance  
U
 1
U =0
Other symbols can be derived by using suitable subscripts for short-
circuit conditions, as given in IEC 60027-1.
207.2 short-circuit reverse siemens S
 I 
Y y
12 12
transfer admittance  
U
 2
U =0
207.3 short-circuit input siemens S
 I 
Y y
21 21
forward transfer  
U
 1
admittance; short-
U =0
circuit input transfer
admittance
...