ISO/IEC 8482:1993
(Main)Information technology — Telecommunications and information exchange between systems — Twisted pair multipoint interconnections
Information technology — Telecommunications and information exchange between systems — Twisted pair multipoint interconnections
Specifies the physical medium characteristics for twisted pair multipoint interconnections in either 2-wire or 4-wire network topology, a binary and bi-directional signal transfer, the electrical and mechanical design of the endpoint system branch cables and the common trunk cable which may be up to 1200 m in length, the component measurements of the integrated type generators and receivers within the endpoint system, the applicable data signalling rate up to 12,5 Mbit/s.
Technologies de l'information — Télécommunications et échange d'informations entre systèmes — Interconnexions multipoints par paire torsadée
General Information
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Standards Content (Sample)
INTERNATIONAL
ISO/IEC
STANDARD 8482
Second edition
19934 2-l 5
Information technology -
Telecommunications and information
exchange between Systems - Twisted
pair multipoint interconnections
- T6kommunications et khange
Technologies de I ’informa tion
- In terconnexions multipoin ts par paire
d ’informations entre syst&mes
torsadbe
Reference number
ISO/1 EC 8482: 1993(E)
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ISO/IEC 8482: 1993(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the Inter-
national Electrotechnical Commission) form the specialized System for
worldwide standardization. National bodies that are members of ISO or
IEC participate in the development of International Standards through
technical committees established by the respective organization to deal
with particular fields of technical activity. ISO and IEC technical com-
mittees collaborate in fields of mutual interest. Other international organ-
izations, governmental and non-governmental, in liaison with ISO and IEC,
also take part in the work.
In the field of information technology, ISO and IEC have established a joint
technical committee, ISO/IEC JTC 1. Draft International Standards adopted
by the joint technical committee are circulated to national bodies for vot-
ing. Publication as an International Standard requires approval by at least
75 % of the national bodies casting a vote.
International Standard lSO/IEC 8482 was prepared by Joint Technical
Committee lSO/IEC JTC 1, Information technology, Subcommittee SC 6,
Telecommunications and information exchange between Systems.
This second edition cancels and replaces the first edition
(ISO 8482:1987), which has been technically revised.
Annexes A and B of this International Standard are for information only.
0 ISO/IEC 1993
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without Permission in writing from the publisher.
ISO/1 EC Copyright Office l Case Postale 56 l CH-1 211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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ISOJIEC 8482:1993(E)
INTERNATIONAL STANDARD
Information technology - Telecommunications and
information exchange between Systems - Twisted pair
multipoint interconnections
- mode of synchronous or asynchronous trans-
1 Scope
mission;
11 This International Standard specifies the
- Signal quality for transmission and reception.
physical medium characteristics for
14 . This International Standard does not specify
- twisted pair multipoint interconnections in either
special environmental conditions, such as galvanic
2-wire or 4-wire network topology in Order to provide
isolation, electromagnetic interference (EMI), radio
for half duplex or duplex data transmission capability,
frequency interference (RFI), and human safety. This
respectively;
may form the subject of a future amendment.
- a binar-y and bi-directional Signal transfer of the
. This International Standard is primarily a
15
interconnected endpoint Systems;
component specif icat ion. lt is not sufficiently
specified for satisfactory interoperation in all possible
- the electrical and mechanical design of the endpoint
configurations. lt is the responsibility of implementors
System branch cables and the common trunk cable,
to ensure that their intended configuration will allow
which may be up to 1 200 m in length;
satisfactory interoperation.
- the component measurements of the integrated
16 This International Standard may be com-
circuit type generators and receivers within the
bined with any appropriate set of functional and
endpoint Systems;
additional environmental characteristics so as to
meet the practical data transmission requirements in
- the applicable data signalling rate up to 12,5 Mbit/s.
the field of local or wide area networks.
12 The defined electrical component charac-
2 Normative reference
teristics and measurements are in close conformance
with the twisted pair Point-to-Point characteristics
The following ITU-T Recommendation contains
given in ITU-T Recommendation V.11.
certain provisions which, through reference in this
text, constitutes provisions of this International
13 This International Standard does not de-
Standard. At the time of publication, the edition
scribe a complete physical interface and has no
indicated was valid. All CCITT Recommendations
functional interface characteristics, such as
and International Standards are subject to revision,
and Parties to agreements based on this International
- number of interchange data and control circuits;
Standard are encouraged to investigate the
possibility of applying the most recent edition of the
- type, size and pin allocation of the endpoint System
recommendation indicated below. Members of IEC
and branch trunk cable connectors;
and ISO maintain registers of currently valid
International Standards. The ITU-T Secretariat
- data and control Signal encoding;
maintains a list of currently valid ITU-T
Recommendations.
- time relations between Signals on the interchange
circuits;
1
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ISO/IEC 8482:1993(E)
V.11 :1988, Electrical 3.6 differential mode voltage: The vector differente
ITU-T Recommendation
of the voltages between each conductor of a
characteristics for balanced double-curren t inter-
Change circuits for general use with integrated circuit balanced interchange circuit and ground or other
stated voltage reference.
equipment in the field of data communications.
NOTE - The differential mode voltage is commonly
referred to as the transverse mode voltage.
3 Definitions
3.7 environmental conditions: Those charac-
teristics of the electrical or physical environment, for
For the purposes of this International Standard the
example EM 1, ground potential differente magnetic
following definitions apply:
fields, altitude, temperature, etc., which may affect
the Operation, with respect to interchange circuits, of
3.1 balanced interchange circuit: An interchange
a DTE or DCE.
circuit which uses two conductors and the differential
mode voltage for transmitting Signals.
3.8 galvanic isolation: The existente of a element
that is non-conductive with respect to the conductivity
3.2 common mode ejection ratio (CMRR ): For
of common mode voltage, between the equipment
balanced interchange circuits, the ratio of an applied
containing a generator and the equipment containing
common mode voltage, &* to the resulting
a receiver of an interchange circuit.
transverse voltage l& (Same as the differential mode
voltage).
3.9 generator: The component of an intercha
nw
circuit that is the Source of the tra nsmitted Signal.
The ratio is normally expressed in decibels as
NOTE - The term generator is used interchangeably with
V
the term driver.
CM Rf? = 20 log p
tr
3.10 generator offset voltage: The d.c. component
NOTE - The rejection ratio depends upon the circuit
of half the vector sum of the voltages between each
termination and should be measured while terminated in
conductor of a balanced interchange circuit generator
normal use.
and its Signal ground reference
3.3 common mode voltage: One half the vector
NOTE - The d.c. component of half the vector sum of the
sum of the voltages between each conductor of a
voltages is t he same as the arithmetic mean of the d.c.
balanced interchange circuit and ground or other
voltages in the above.
stated voltage reference.
3.11 ground Signal: The generator/receiver Signal
NOTE This voltage may be a transmitted (or received)
voltage reference.
Signal or noise intereference. In the latter case, this
voltage is generally not the same as the voltage, which is
3.12 ground earth: The voltage reference
sometimes referred to as common mode voltage, that may
established by conductive components having a
exist (in a common mode) between the ends of an
conductive path to earth in the vicinity of the
interchange circuit pair as a result of induction or ground-
equipment including the generator/receiver.
reference potential differente.
NOTE - Earth ground is generally synonymous with, and
3.4 Cross-talk loss (near end): For two interchange
the same as, frame or building ground or protective
circuits used for transmission in opposite directions,
ground.
the ratio, expressed in decibels, of the voltage
transmitted on one interchange circuit to the resulting
3.13 ground potential differente: The differente
voltage (Cross-talk) at the receive end of the other
between the Signal ground Potentials of the generator
interchange circuit.
and the receiver of an interchange circuit.
3.5 cross-talk loss (far end): For two interchange
The potential is the Same as the differente in the
circuits used for transmission in the Same direction,
earth ground potential differente only if the Signal
the ratio, expressed in decibels, of the voltage
ground is connected to earth ground at both the
transmitted on one interchange circuit to the resulting
generator and the receiver.
voltage (Cross-talk) at the receive end on the other
interchange circuit.
2
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lSO/IEC 8482:1993(E)
3.19 site conditions: The
3.14 induced noise: An interfering voltage that is in- environmental conditions
interchange circuit by for a given site.
troduced into an
electromagnetic induction from currents in other
3.20 surge voltage resistance: The ability of an
conductors.
interchange circuit to function normally after being
For balanced interchange circuits induced voltages subjected to surges having peak voltages up to some
specified value.
generally appear in the common mode.
NOTE - Surge voltage resistance is sometimes referred to
3.15 interchange circuit: The circuit, including a
as surge immunity.
generator, a receiver and interconnecting media, that
provides for the interchange of Signals across an
3.21 surge voltage: A transient voltage wave
DTE/DCE,
interface, for example DTE/DTE,
appearing on an interchange circuit as a result of
DCE/DCE.
induction or other phenomenon and having a
relatively high value and short duration.
3.16 interchange Point: The Point in an interchange
circuit at which the specified electrical characteristics
lt is normally acceptable for such surges to
of the circuit apply and should be measured.
errors or malfunctions.
NOTE - The interchange Point usually defines the line of
NOTE - Surges are normally specified with the intent of
demarcation between equipment and is usually the
assuring that equipment will not be damaged by such
location of an interface connector.
unusual conditions.
3.17 receiver: The component of an interchange
3.22 unbalanced interchange circuit: An
circuit that provides for the detection of interchange
interchange circuit that uses one conductor together
circuit Signals at the receiving equipment.
with a second return conductor, normally Signal
ground, which is used in common by several circuits.
3.18 rise time: The time required for a generator
output Signal voltage to Change from a value
characteristic of one state to a value characteristic of
a second state.
4 Symbolic representation of an in-
terchange circuit (see figure 1)
lt is most often specified as the time for the Signal
voltage to pass between the 10 % and 90 % Points of
The symbolic representation of an interchange circuit
the wave form.
is in principle as given in ITU-T Recommendation
NOTES v.ll. However, the generator specified in this
International Standard includes an additional control
1 Rise time is normally dependent on the load and
to place the device into the active state or the
is usually specified for a specific test termi nation.
inactive, high impedance Zero voltage state. This
addition is shown in the symbolic representation
2 For unbalanced generators, the time for the
reproduced in figure 1.
Change from an ON or active state to an OFF or inactive
state is sometimes referred to as the “fall time ”.
3
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ISO/IEC 8482:1993(E)
Balanced
I
Generator
Receiver
I
interconnecting cable I
I
I
I
High
impedance
control
V
9
I
I
Generator Receiver
interchange Point interchange Point
V
Generator output voltage between Points A and B
ab
V = Generator voltage between Points A and C
ac
= Generator voltage between Points B and C
‘bc
= Ground potential differente
vY
= Cable termination resistor
Rt
A, B and A ’, B’ = Interchange Points
c, C’ = Zero volt reference interchange Points
(Signal ground)
1 Two interchange Points are shown. The output characteristics of the generator, excluding any interconnecting cable, are defined at the “generator
interchange Point ”. The electrical characteristics to which the receiver must respond are defined without the cable termination resistor at the “receiver
interchange Point ”.
2 Points C and C’ may be interconnected and further connected to protective ground if required by national regulations.
Figure 1 - Symbolic representation of interchange circuit
The balanced trunk cable shall be terminated by a
5 Interconnection configurations (see
termination resistor at each end. This facilitates the
figures 2 and. 3)
generator/receiver load measurements defined in
6.1.2. For connection of the endpoint Systems to the
In general, the interconnection configuration consists
trunk cable, a branchitrunk cable connector should
of one balanced trunk cable,. which may be up to
be used. The connector(s) at each end of the trunk
1 200 m in length, and several balanced branch
cable shall accommodate the termination resistor(s).
cables, each connecting an individual endpoint
System to the common trunk cable. The branch cable
Balanced cables may be shielded if required by local
connection Points may be spaced as appropriate. A
regulations. lt may also be necessary to extend
branch cable should be kept as short as possible and
shielding across the branch/trunk cable connectors.
in any case not exceed 1 m in length.
4
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lSO/lEC8482:1993(E)
Depending on the type of multipoint Operation, either transmission, while figure 3 Shows a four wire
a two wire or a four wire interconnection configuration multipoint configuration for either half duplex or
may be used. For example, figure 2 Shows a Wo wire duplex data transmission.
multipoint configuration for half duplex data
Balanced two-wire trunk cable
/-\
.---- -----v----v--
-------- $-i---p --
11
I
R
I R
t ! t
1 !
~~~~o-wires $ G ~Ii~
Endpoint System Endpoint System Endpoin
t System
Figure 2- Two-wire multipoint configuration
Balanced four-wire trunk cable
---------- ---------- +c+-- -- 1)
-- e---v
f
t t I I
I -
, T
R
t
I
1 7
I
w
R
I
t
I
/w
r
-
T
I I I
1-r I I
.
Endpoint System Endpoint System Endpoint System
Legend : L Signal ground I, - Protective ground
NOTES
.
1) Interconnection of the endpoint System Signal ground is optional and depends on local regulations.
2) Branch cable shield is optional and, when provided, it connects to the endpoint System protective ground, which may be further connected to the
Signal ground.
3) Trunk cable shield is optimal and, when provided, it connects to a protective ground at one place. Interconnection of shield to branch cable
shields may be necessary.
Figure 3 - Four-wire multipoint configuration
5
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ISO/IEC 8482 1993(E)
6.1.2 UL determination of the endpoint
6 Load on the multipoint medium
Systems (.see figures 5 and 6)
Esch endpoint System represents a load to the
multipoint medium. The load consists of a passive When measuring the currentlvoltage characteristics
generator and/or a receiver with associated internal at the disconnected branchitrunk cable connector of
wiring and a balanced branch cable as shown in one endpoint System, the measured generator shall
figures 2 and 3. In accordance with the multipoint half be in the inactive state. The measurement
duplex data transmission principle, only one configuration is shown in figure 5.
The
generator- is in the active state at a given time. current/voItage measurement corresponds to that of
the V.11 receiver input in ITU-T Recommendation
Successful Operation requires specification of the V.ll, i.e. with the voltage Via (or Yb) ranging
load in terms of dc. loading and a.c. loading. For d.c. between - 7 V and + 12 V, while Yb (or via) is held
loading, the component specification in clauses 8 and at Zero Volts, the resulting input current Iia (or /ib)
9 are selected such that an active generator tan should remain within the shaded range shown in
drive the interconnecting trunk cable, terminated at figure 4. These measurements apply with the power
each end with not less than 120 Q and 32 so-called supply of the generator and/or receiver in both the
power-On and power-Off conditions.
Unit Loads (ULs), representing the total load of all
endpoint Systems. The value of 1,O UL is defined in
To determine UL from the measurements, the slope
6.1 .l.
of the bounds of the current limit of one UL, see
figure 4, shall be modified to the minimum slope
61 .
Specification of d.c. loading
required to fully contain the current/voltage
characteristics, while the - 3 V and + 5 V intercept
The d.c. loading specification limits the current of an
Points are maintained. The actual value of UL is then
active generator to a practical value. For this reason,
equal to the larger of the two ratios of the actual
a hypothetical Unit Load (UL) is defined for a
current to the one UL current at the - 7 V and + 12 V
current/voItage measurement.
Points (see the two examples of UL value
determinations in figure 6).
UL definition (sec figure 4)
6.1.1
The slopes of the currents should be positive to lower
The value of 1,O UL is defined by a current ranging
the possibility of oscillations f rom negative
between - 0,8 mA and + 1,0 mA when varying the
resistance.
voltage between - 7 V and + 12 V. The
correspondent current/voltage diagram is shown in
When adding all measured UL values, the sum shall
figure 4.
not exceed 32,0.
The voltage range takes into account the output and
6.2 a.c. loading
offset voltage of the generator, the common mode
and internal voltage of the receiver and the power
The a.c. loading on the multipoint medium affects the
supply voltage.
received Signal quality. The determining factors, such
as cable characteristics, type of encoding, etc., are
I
i
Load of
endpoint
System
V
i
Current limit of 1,0 UL
Figure 4- Fiaure 5 - Input currentlvoitacre measurement
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ISO/IEC 8482:1993(E)
I
i
Example 0,8 UL
+0,75 mA
= 0,75
+l,O mA
-0,64 mA
= 0,8
-0,8 mA
+ 1,2 mA
= 1,2
+ 1,0 mA
I
i
+1,2mA
-0,9 mA
Example 1,2 UL
= 1,125
-0,8 mA
Figure 6 - Ul value determination
application dependent and therefore beyond the
The tests are made for either binar-y state, whereby
scope of this International Standard.
Some for the magnitude of the voltage specifications both
guidance, however may be obtained form annex B.
Symbols IV1 and lvl are used, respectively.
81 . Open circuit voltage,
V
0
7 Polarities and significant levels
The voltage, when measured
in accordance with
The generator polarities and receiver significant
figure 7, shall be, between the
levels have closer tolerantes than those specified in
ITU-T Recommendation V.11.
- output terminals A, B: 1,5V 5 IVO1 or Ivo1 < 6,OV
Table 1 - Receiver differential significant levels - terminals A, C and B, C:
Iv,,l or IVo,lor ltal or I<,l< 60 V
-vg s- WV v*, -vg <+ 0,2v
-
b
82 l Offset voltage, VS
Data circuits MARK, 1 SPACE, 0
The voltage, when measured in accordance with
figure 8, shall be, between the
Control and OFF ON
- load centre and terminal C:
OV < V, or v,S < 3,0V
timing circuits
- binary states, the differente:
I V,, -v,i 10,2v
8 Generator characteristics
83 . Terminated output voltage, l(
The generator
...
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