ISO/TR 7477:1985

Data communication — Arrangements for DTE to DTE physical connection using V.24 and X.24 interchange circuits

Describes various arrangements for interconnection of Data Terminal Equipment (DTE), without intermediate Data Circuit-terminating Equipment, concerning electrical, mechanical, and functional characteristics. Applies to DTEs with interface circuits standardized in CCITT Recommendation V.24 for data transmission over telephone networks or with interface circuits standardized in CCITT Recommendation X.24 for transmission over public data networks. Applies primarily to DTEs employing the balanced electrical characteristics of CCITT Recommendation V.11 (X.27) for data signalling rates up to 10 Mbit/s.

Transmission des données — Arrangements pour la connexion physique ETTD à ETTD utilisant des circuits de jonction V.24 et X.24

General Information

• Status: Withdrawn
• Publication Date: 02-Oct-1985
• Withdrawal Date: 02-Oct-1985
• ICS: 35.100.10 - Physical layer
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 06-Jun-1996

Relations

• Revised: ISO/IEC 8481:1996 - Information technology — Telecommunications and information exchange between systems — DTE to DTE direct connections
• Effective Date: 15-Apr-2008
• Consolidated By: ISO 7439:2002 - Copper-bearing intra-uterine contraceptive devices — Requirements, tests
• Effective Date: 06-Jun-2022

Standards Content (Sample)

TECHNICAL REPORT 7477-1985 (EI
Published 1985-09-15
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.MEXt(LLYHAPOAHAR OPrAHM3ALWlR I-IO CTAH,4APTM3AWlM~ORGANISATlON INTERNATIONALE DE NORMALISATION
Data communication - Arrangements for DTE to DTE
physical connection using V.24 and X.24 interchange
circuits
Transmission des donnhes - Arrangements pour Ia connexion physique ETTD 5 ETTD utilisant des circuits de jonction V.24
et X.24
ISO (the International Organization for Standardization) is a worldwide federation of national Standards bodies (ISO member bodies).
The work of preparing International Standards is normally carried out through ISO technical committees. Esch member body
interested in a subject for which a technical committee has been established has the right to be represented on that committee.
International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
The main task of ISO technical committees is to prepare International Standards. In exceptional circumstances a technical committee
may propose the publication of a technical report of one of the following types :
-
type 1, when the necessary support within the technical committee cannot be obtained for the publication of an International
Standard, despite repeated efforts;
-
type 2, when the subject is still under technical development requiring wider exposure;
-
type 3, when a technical committee has collected data of a different kind from that which is normally published as an
International Standard (“state of the art”, for example).
Technical reports are accepted for publication directly by ISO Council. Technical reports types 1 and 2 are subject to review within
three years of publication, to decide if they tan be transformed into International Standards. Technical reports type 3 do not
necessarily have to be reviewed until the data they provide is considered no longer valid or useful.
ISO/TR 7477 was prepared by Technical Committee ISO/TC 97, Information processing Systems.
The reasons which led to the decision to publish this document in the form of a technical report type 2 are explained in the
Introduction.
0 Introduction
Consideration has been given to the existing DTE/DCE interface specifications which provide the mechanical, electrical, functional
and procedural characteristics for the physical interconnection of DTEs to modems in telephone networks (CCITT V-series
Recommendations) or to termination units of data networks (CCITT X-series Recommendations); a unique ISO requirement exists to
further define the direct interconnection of such DTEs without intervening telecommunication facilities.
Also, in the DTE to DTE physical connection, the distance of interconnection may be considerably greater when compared with the
usual short telephone/data network interconnections; an additional Option to permit the alternate use of balanced type electrical
characteristics is therefore required.
UDC 681.3 : 621.316.5 Ref. No. ISO/TR 7477-1985 (E)
Descriptors : data processing, data transmission, data terminal equipment, data communication equipment, electric connectors, specifications.
c
0 International Organkation for Standardkation, 1985 0
3
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Printed in Switzerland Price based on 8 pages

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ISO/TR 7477-1985 (EI
transmission, Signal element timing in lieu of the network clocks must
In the case of synchronous variety of arrangements to provide
also be supported.
In view of further developments of interfaces for future telecommunication facilities by the CCITT, an appropriate time for reconsider-
ing the publication of an International Standard may be at the end of the CCITT 1985 to 1988 study period.
This Technical Report deals with the interconnection of Data Terminal Equ ipme lnt (DTE) without any Signal conversio whereby a
In,
DTE is not attached to Data Circuit-terminating Equipment (DCE) which is part of a telecommunication faci lity.
The desired DTE to DTE direct connection may be totally located at the user’s territory. The aim being to relate these interconnections
in Order Proliferation.
to the elements of the CCITT recommended/ I so standardized DTE/ DCE interfaces, to avoid equipment
1 Scope and field of application
This Technical Report describes various arrangements for the interconnection of Data Terminal Equipment (DTE), without in-
termediate Data Circuit-terminating Equipment (DCE), in terms of electrical, mechanical, and functional characteristics.
This Technical Report applies to DTEs with interface circuits standardized in CCITT Recommendation V.24 for data transmission over
telephone networks or with interface circuits standardized in CCITT Recommendation X.24 for transmission over public data
networks.
The interconnections are restricted to Point-to-Point connections. Extension to multipoint configurations requires further study.
This Technical Report applies primarily to DTEs which employ the balanced electrical characteristics of CCITT Recommendation V. 11
(X.27) for data signalling rates up to 10 Mbit/s. Additionally, it may be applied to DTEs employing the unbalanced electrical
characteristics of CCITT Recommendation V.10 (X.26) for data signalling rates up to 100 kbit/s and of CCITT Recommendation V.28
for data rates below 20 kbit/s. Interworking between a DTE employing V.10 (X.26) and a DTE employing V.11 (X.27) or with a DTE
employing V.28 is permitted.
The interconnection may be used for startstop and synchronous transmission. For synchronous transmission, the Signal element tim-
ing may be provided by either one DTE, both DTEs, or by an external Signal element timing Source which is inserted as intermediate
equipment.
2 References
ISO 2110, Data Communication - 25pin DTE/DCE interface connector and pin assignments.
ISO 4902, Data communication - 37-pin and 9-pin DTE/DCE interface connectors and pin assignments.
ISO 4903, Data communication - Spin DTE/DCE interface connector and pin assignments.
Elec trical charac teris tics for unbalanced double- curren t in terchange circuits for general use
CCITT Recommendation V. IO (or X.26),
with in tegra ted circuit equipmen t in the field of data communica tions.
CCITT Recommendation V. 11 (or X.27), Electrical characteristics for balanced double-current interchange circuits for general use
with integrated circuit equipment in the field of data communications.
CCITT Recommendation V.24, List of definitions for interchange circuits bemeen da@ terminal equipment (DTE) and data circuit-
terminating equipment (DCE).
CCITT Recommendation X.24, List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-
terminating equipment (DCE) on public data networks (PDN).
CCITT Recommendation V.28, Electrical characteristics for unbalanced double-current interchange circuits.
3 lnterconnection configurations
Three types of DTE to DTE interconnection configurations are considered for Point-to-Point connections with interfaces according to
.
CCITT Recommendations V.24 and X.24. They are shown in figure 1.
t
2

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lSO/TR 7477-1985 (El
There are two lines of demarcation between the two interconnecting DTEs, one located at each DTE connector. The adaptor and any
cable linking these two DTE connectors are not part of either DTE.
Intermediate balanced pair cable may be provided with a length mainly dependent on the Parameters of the electrical characteristics of
the interchange circuits.
4 Interchange circuit requirements
The interchange circuit requirements are specified in terms of electrical, functional, mechanical, and interchange Point Cross-over
characteristics.
4.1 Electrical characteristics
The electrical characteristics of CCITT Recommendation V. 11 are preferred in all configurations.
Recommendation V. 11 (X.27) gives guidance to operational constraints imposed by the length, balance, and terminating resistance of
the interconnecting cable in relation to the data signalling rate. With additional considerations, longer distances may be possible.
DTEs employing the unbalanced electrical characteristics, with the category 1 receiver configuration of CCITT Recommendation V. 10
(X.26), are also permitted for applications up to 100 kbit/s. Reduced performante in terms of cable length may be experienced,
however. Reference should be made to CCITT Recommendation V.10 (X.26) for constraints imposed by length of interconnecting
cable in relation to data signalling rate.
Interoperation between DTEs employing V.10 (X.26) generators on one side of the DTE/DTE interface and V.11 (X.27) generators on
the other side of the DTE/DTE interface is permitted as described in CCITT Recommendation V.10 (X.26).
In addition, DTEs using the electrical characteristics for unbalanced double-current interchange circuits of CCITT Recommendation
V.28 are permitted for applications below 20 kbit/s. The distance capability however is limited.
Interoperation between a DTE employing V. 10 (X.26) electrical characteristics and a DTE employing V.28 characteristics is also per-
mitted, provided the precautions outlined in annex D of ISO 4903 are observed.
Configuration :
Lines of demarcation
I
I I
I
.
V.24
V.24
V.241V.24
DTE
DTE
.
37 pin or 25 pin
/
connectors
A
X.24
X.24
X.24lX.24
DTE b
DTE
15 pin
connectors
X.24
V.24
X.24lV.24
DTE DTE
15/37 pin or 25 pin
adaptor
Figure 1 - DTE interconnection configurations

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ISO/TR 7477-1985 EI
Table 1 - List of V.24 circuits for DTE interconnection
Circuit description/remarks
1
I
- - -
1 1 f Cable shield 1)
!
I
102 C - C’
C - C’ 19 7 / Signal ground (see 4.6)
I
1 / I
!
103 A - A’ A - A’
4 2 i Transmitted data
B - B’ C - B’ 22 ;
1
a
104 j A - A’
A - A’ 6 3 ; Received data
‘
B - B’ C - B’
24
,
A - A’ 7 4 / Request to send2)
t
j C - B’
Io5 25
I
106 i A - A’ 1 A-A’ * 9 5 i Ready for sending
B - B’ C - B’ 27
I
I I
107 A - A’ A -A’ j 11 6 Data set ready
!
-8’ 1
B - B’ C
29
108 ’ A - A’ ! A - A’ 12 20
1 Connect data set to line/Data terminal ready
B - B’
C - B’ 30
109 ’ A - A’
A - A’ 13 8 : Data channel received line Signal detector
i /
B - B’ C -B’ 1 31
I
113 1 A - A’ 1 A - A’ 17 24 ; Transmitter Signal
element timing, DTE source3)
1 B - B’ j C-B’ 35 l
1
114 ; A - A’ 1 A-A’ [
5 15 ; Transmitter Signal element timing, DCE source3)
I
j C-B’ /
B - B’ 23
I
- A’ 1 A - A’
115 I A
Receiver Signal element timing
j C - B’
- B’
B
1
I
1) Pin 1 is for connecting the shields between tandem sections of shielded interface cable.
2) This circuit is optionally provided by th
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