ISO 21792:2019

INTERNATIONAL ISO
STANDARD 21792
First edition
2019-08
Ships and marine technology —
Navigation and ship operations —
Guidelines for onboard telephone
equipment
Navires et technologie maritime — Navigation et opérations
maritimes — Lignes directrices concernant le matériel téléphonique
embarqué
Reference number
ISO 21792:2019(E)
©
ISO 2019

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ISO 21792:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO 21792:2019(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Types of telephones . 1
4 General characteristics . 2
4.1 General . 2
4.2 Automatic telephones . 3
4.3 Common battery telephones . 4
4.4 Battery-less telephones . 4
4.5 Sound-powered telephones . 4
5 Quality . 4
5.1 General . 4
5.2 Measures to prevent howling . 4
5.3 Measures to suppress noise . 4
6 Data recommendations — Automatic telephones . 5
6.1 General . 5
6.2 Multifunction telephones . 5
6.2.1 Signal condition . 5
6.3 Analog telephone . 5
6.3.1 Signal condition . 5
6.3.2 Output signal . 5
6.3.3 Input signal . 6
6.4 Connection to external communication equipment . 6
6.4.1 Signal condition . 6
6.4.2 Output signal . 6
6.4.3 Input signal . 6
7 Installation . 6
7.1 General . 6
7.2 Environment . 6
7.2.1 Temperature . 6
7.2.2 Vibration and swinging motion . 7
7.2.3 Dust and water protection . 7
7.3 Explosion protection . 7
7.4 Cabling . 7
8 Performance tests . 8
8.1 General . 8
8.2 Shop test . 8
8.3 Onsite test .11
8.3.1 General.11
8.3.2 Automatic telephones .11
8.3.3 Common battery telephones, battery-less telephones and sound-powered
telephones .13
9 Maintenance .14
9.1 General .14
9.2 Routine maintenance .14
9.3 Periodic maintenance.14
9.3.1 Method .14
9.3.2 Measures against corrosion .15
9.4 Periodic maintenance programme and procedures .15
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ISO 21792:2019(E)

9.4.1 Automatic telephones .15
9.4.2 Common battery telephones, battery-less telephones and sound-powered
telephones .16
9.5 Replacement period .16
Bibliography .18
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ISO 21792:2019(E)

Foreword
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. Each 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.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 6, Navigation and ship operations.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
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ISO 21792:2019(E)

Introduction
Onboard telephone equipment generally includes automatic telephones, common battery telephones,
battery-less telephones and sound-powered telephones.
Until now, there have been no comprehensive standards for onboard telephone equipment provided by
different manufacturers, and this has impeded the equipment improvements of reliability.
This document will promote sharing common understanding among all parties involved, including the
manufacturers, engineering companies, shipbuilders and ship owners.
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INTERNATIONAL STANDARD ISO 21792:2019(E)
Ships and marine technology — Navigation and ship
operations — Guidelines for onboard telephone equipment
1 Scope
This document provides general and specific recommendations related to the quality of communication,
connectivity, installation, performance and maintenance of onboard telephone equipment, including
automatic telephones, common battery telephones, battery-less telephones and sound-powered
telephones.
It also specifies requirements for the related performance tests (shop tests and onsite tests) and for the
maintenance tests.
It is not applicable to digital telephones, LAN (VoIP) telephones, and wireless telephones.
NOTE These telephones are excluded because they were under development during the elaboration of this
document so that their specifications remained to be determined.
Table 1 further illustrates the applicability of this document.
Table 1 — Applicability of this document
Signal
Type of connection
Analog Digital
Wired X n.a.
Wireless n.a. n.a.
X: covered in this document.
n.a.: not applicable.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1 Types of telephones
3.1.1
automatic telephone
telephone commanded under an automatic telephone exchanger (3.3)
Note 1 to entry: Automatic telephones can be classified into four types — desk, wall-mounted, flush-mounted
and portable — based on their structural appearance.
Note 2 to entry: Automatic analog telephones are called "automatic telephones" in this document.
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3.1.2
common battery telephone
telephone powered by a DC power supply (DC24V)
Note 1 to entry: Common battery telephones are classified into two types — “selective” and “direct” — based on
their connectivity.
Note 2 to entry: Common battery telephones can be classified into four types — desk, wall-mounted, flush-
mounted, and portable — based on their structural appearance.
3.1.3
battery-less telephone
telephone fitted with a hand crank generator for communicating by voice, amplified by self-
generated power
Note 1 to entry: Battery-less telephones are classified into two types — “selective” and “direct” — based on their
connectivity.
Note 2 to entry: Battery-less telephones can be classified into four types — desk, wall-mounted, flush-mounted,
and portable — based on their structural appearance.
3.1.4
sound-powered telephone
battery-less telephone (3.1.3) not requiring an external power source for conversation (talk circuit)
Note 1 to entry: A hand crank generator is only used for signalling actions.
Note 2 to entry: Sound-powered telephones can be classified into four types — desk, wall-mounted, flush-
mounted, and portable — based on their structural appearance.
3.2
automatic telephone equipment
system that connects automatic telephones (3.1.1) to an automatic telephone exchanger (3.3), thereby
enabling telephonic ringing and telephonic conversation between any two automatic telephones
through selection signals (such as push button or dial pulse dialling)
3.3
automatic telephone exchanger
telephone exchanger that uses automatic telephones (3.1.1), made durable to withstand typical
shipboard vibration and environments
Note 1 to entry: This is also available for public announcements by way of a PA system. Through this, the
automatic telephone is able to communicate with land telephones via SATCOM or INMARSAT, etc.
3.4
howling
unpleasant noise caused by audio feedback due to repeated amplification by the amplifier of the voice
input, that impedes intelligible conversation
4 General characteristics
4.1 General
The classification and connection of telephones are shown in Table 2 and Figure 1.
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ISO 21792:2019(E)

Table 2 — Classification of telephones
Type of
Connection Amplified DC power supply
telephone
Automatic
Multiple X X
telephone
Common battery
X X
telephone
Battery-less
Direct/Selective X n.a.
telephone
Sound-powered
n.a. n.a.
telephone
X: existing configuration.
n.a: not applicable.

NOTE The telephones covered in this document are written in white letters on black.
Figure 1 — Connection of telephones
The onboard telephone equipment includes automatic telephones, automatic telephone exchanger,
common battery telephones, battery-less telephones and sound-powered telephones.
The equipment should ensure accurate transmission and reproduction of the caller voice signals.
4.2 Automatic telephones
The automatic telephone equipment enables calling between onboard and outboard telephone
equipment by connecting to outboard communication systems (such as INMARSAT, VSAT, cellular
phones, and landline telephones). It also enables paging broadcasts from the telephone equipment by
coupling with a public addresser.
The automatic telephone exchanger should be able to withstand typical vibration and swinging motions
(pitch and roll) for use in a shipboard environment.
The automatic telephone exchanger should comply with ISO 19847 and ISO 16425.
Electric source for the automatic telephones should be supplied by both AC power and DC power
(DC24V). In case the AC power is lost, the telephones can switch to the DC power supply automatically.
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4.3 Common battery telephones
Selective common battery telephones permit telephonic ringing and telephonic conversation between
any two devices.
Direct common battery telephones only permit telephonic ringing and telephonic conversation between
parent and child telephones (such as 1:1, 1:2, and 1:3 configurations).
A DC power supply (DC24V) is required for common battery telephones.
4.4 Battery-less telephones
Battery-less telephones are able to use their built-in generator to call other telephones, even if power is
not supplied from an external source.
If a complete power failure occurs on a ship, the battery-less telephone (or sound-powered telephone)
may be the only emergency system available for communication.
4.5 Sound-powered telephones
In high noise environments, the hand crank generator may also power a latching circuit at a remote
station that augments the hand crank generator powered signalling circuit with an externally powered
audible or visual signalling device.
The hand crank generator powers the signaling circuit to notify another station. Sound-powered
telephones use “common talk” (everyone hears the conversation) for all stations on the circuit.
Sound-powered telephones are classified as direct call and selective call.
If a complete power failure occurs on a ship, the sound-powered telephone (or the battery-less
telephone) may be the only emergency system available for communication.
5 Quality
5.1 General
When dealing with onboard telephone equipment, the measures given in 5.2 and 5.3 should be taken to
ensure the accurate transmission of caller voice information.
5.2 Measures to prevent howling
Howling may occur due to the position and directivity of handsets and speakers of the onboard
telephone equipment.
The following measures should be taken to prevent howling.
a) The microphones and speakers should be kept sufficiently far away from each other with their
amplification loop broken to prevent howling.
b) In the case of paging broadcasts from the automatic telephone, the telephones and speakers should be
kept sufficiently far away from each other, and a handset designed to prevent howling should be used.
5.3 Measures to suppress noise
Noise may increase if the voice signal of the telephone receives interference from other electrical circuits
(such as power lines). The following measures should be taken to suppress the generation of the noise.
a) For voice signal cables such as the microphone, shielded cables that can prevent the noise due to
electromagnetic induction from other lines should be used.
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b) The telephones should be kept sufficiently away from the source of the noise in order to avoid its
adverse impact.
c) Automatic telephone may use twisted-pair cables rather than multicore cables for preventing the
noise due to electromagnetic induction.
d) If a DC power source is used for common battery telephones, the ripple component from the full-
wave rectification of the built-in AC power supply presents in the charging and discharging board,
and the high frequency component generated by the switching-device power controller, may cause
electrical noise. Common battery telephones are adversely affected by the noise from the DC power
source. In order to prevent the noise, an isolated DC/DC converter should be used to power the
common battery telephone.
e) Attention should be paid to the wiring of cables (refer to 7.4).
f) Particular attention should be paid to the routing of sound-powered telephone cabling. Sound-
powered telephones cabling should be routed away from equipment that may generate large
electromagnetic signals, and/or cabling that carries large power currents. Examples of such
equipment include: electrical motors, switchboards, spark-ignition engines, power lines.
g) When installed in spaces with high levels of background noise that severely impact the ability of an
operator to maintain audible telephonic conversation, a sound absorbing chamber large enough to
place the operators head inside or an appropriate headset unit should be provided.
6 Data recommendations — Automatic telephones
6.1 General
Connection between automatic telephones and onboard communication systems should be in
accordance with the data recommendations given in 6.2 to 6.4. They are applicable only to automatic
telephones.
6.2 Multifunction telephones
6.2.1 Signal condition
Multifunction telephones should meet the requirements mentioned in the exchanger specifications.
Products from the same manufacturer as that of the exchanger should be used, otherwise compatibility
should be confirmed.
6.3 Analog telephone
6.3.1 Signal condition
The open-circuit voltage should be DC 24 V/48 V.
The open-circuit voltage should be compatible with loop-start signaling.
6.3.2 Output signal
The selection signal should be a PB signal.
The selection signal should comply with ITU-T Q.23/Q.24.
The selection signal should also be compatible with DP signals.
NOTE PB signal (push button dial signal), DP signal (dial pulse signal).
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6.3.3 Input signal
The ringing signal should be a bell signal.
The ringing signal should be of AC 65 V–100 V and 16–25 Hz.
The audible ring tone should be no less than 80 dB under high levels of background noise area.
The ringing signal may be a bell signal or other distinctive tone that is not confused with other signals.
6.4 Connection to external communication equipment
6.4.1 Signal condition
The open-circuit voltage should be DC 24 V/48 V.
The open-circuit voltage should be compatible with loop-start signaling.
A line inversion function of central office line should be implemented for the call initiation signal.
6.4.2 Output signal
The selection signal should be a PB signal.
The selection signal should comply with ITU-T Q.23/Q.24.
The selection signal may also be compatible with DP signals.
6.4.3 Input signal
The ringing signal should be a bell signal.
The ringing signal should be of AC 65 V–100 V and 16–25 Hz.
7 Installation
7.1 General
The environment for onboard telephone equipment used in onboard communication systems differs
from that for land communication systems; hence, it is necessary to pay attention to external factors
such as water, heat, vibration and swinging motion.
Furthermore, the environment of the onboard telephone equipment should be tested in accordance
with 8.2.
Compliance with IEC 60945 and IEC 60092-101 should be met, after considering the environment in
which the system is to be installed.
7.2 Environment
The equipment used in the onboard telephone equipment should be installed after considering the
environmental requirements (such as ambient temperature and ambient humidity) recommended by
the manufacturer for each component of equipment.
7.2.1 Temperature
The onboard telephone equipment should not be installed near equipment that emits heat.
It should not be located in places where there are sudden fluctuations in temperature.
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In addition, care should be taken not to install the equipment near places where the temperature is too
high (such as the top of a boiler) or too low (such as a freezer).
7.2.2 Vibration and swinging motion
In order to ensure that the equipment is not adversely affected by external vibration, the equipment
should be placed sufficiently far away from the source of vibration, or anti-vibration measures should
be implemented.
The automatic telephone exchanger should be protected and made durable to withstand typical
vibration and swinging motion (pitch and roll) for use in a shipboard environment. The exchanger
should have a terminal connecting the wiring of the telephone units. “Punch-down” terminal points
are insufficient for shipboard use due to vibration. Hard-wired, screw down terminal points are
recommended.
In all cases, telephone should have a means for preventing the handset from coming off-hook during
adverse sea conditions, such as a handset retainer clip, bracket, or other locking mechanism.
7.2.3 Dust and water protection
Equipment whose degrees of protection is appropriate to the location of installation should be set up.
The location environment and degrees of protection should comply with IEC 60529.
7.3 Explosion protection
In explosion risk areas, explosion protection equipment that is appropriate to the installation
environment should be used.
The explosion proof circuit cables should be isolated adequately from other general electrical systems.
In particular, the wiring of intrinsically safe circuits may become dangerous due to electromagnetic/
electrostatic induction if they come in contact with other circuits. Hence, care should be take
...