ISO 10330:2002

INTERNATIONAL ISO
STANDARD 10330
Second edition
2002-09-01
Photography — Synchronizers, ignition
circuits and connectors for cameras and
photoflash units — Electrical
characteristics and test methods
Photographie — Interrupteurs synchronisés, circuits d'amorçage et
connecteurs pour appareils de prise de vue et sources d'éclairs —
Caractéristiques électriques et méthodes d'essai

Reference number
©
ISO 2002
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ii © ISO 2002 – All rights reserved

Contents Page
Foreword . iv
Introduction. v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Requirements . 2
4.1 Polarities for synchronizer terminals and ignition circuit terminals . 2
4.2 Voltage across and current through synchronizer terminals and ignition circuit terminals. 2
4.3 Ignition circuit operation . 4
4.4 Dynamic characteristics of synchronizer. 4
4.5 Synchronizer leakage current. 5
4.6 Electrical characteristics of cable . 5
5 Test methods . 6
5.1 Ignition circuit operation . 6
5.2 Synchronizer dynamic characteristics . 7
5.3 Synchronizer leakage current. 7
Annex A (normative) Requirements and test methods . 9
Annex B (informative) Additional information . 11
Bibliography. 17

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted
by the technical committees are circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 10330 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 10330:1992), of which it constitutes a minor revision.
iv © ISO 2002 – All rights reserved

Introduction
When a camera is used in conjunction with a photoflash unit, the photoflash unit can fail to fire, depending upon the
combination. The possible causes include a failure of the camera or photoflash unit, poor electrical contact at the
connection between both, and the signal transferred to the photoflash unit for firing it being improper.
INTERNATIONAL STANDARD ISO 10330:2002(E)

Photography — Synchronizers, ignition circuits and connectors
for cameras and photoflash units — Electrical characteristics and
test methods
1 Scope
This International Standard specifies the electrical requirements of the camera synchronizer, the ignition circuit in
the photoflash unit and the cable to connect these, and the test methods to secure positive firing of the photoflash
unit.
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.
ISO 516:1999, Photography — Camera shutters —Timing
ISO 518:1977, Photography — Camera accessory shoes, with and without electrical contacts, for photoflash lamps
and electronic photoflash units
ISO 519:1992, Photography — Hand-held cameras — Flash-connector dimensions
ISO 8581:1994, Photography — Electronic flash equipment — Connectors to synchro-cord
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
synchronizer
device provided in a camera or shutter unit which fire the photoflash unit in synchronization with the operation of
the camera shutter and which consists of synchronizer terminals, a synchronization switch and a circuit that
connects them
NOTE For details of synchronization, refer to ISO 516.
3.2
synchronizer terminals
part of the synchronizer which couples the camera or shutter unit with the photoflash unit as does the accessory
shoe with electrical contacts defined in ISO 518 and the socket defined in ISO 519
3.3
ignition circuit terminals
parts of the photoflash unit which are connected to the synchronizer terminals to couple the camera or shutter unit
with the photoflash unit to permit firing operation, as does the foot with electrical contacts defined in ISO 518, the
plug defined in ISO 519 and the sockets defined in ISO 8581
3.4
synchronization switch
switch provided for firing the photoflash unit
NOTE It may be a mechanical or electronic switch.
3.5
synchronizer leakage current
current flowing through the synchronizer when the specified voltage is applied across the synchronizer terminals
with the synchronization switch turned off
3.6
dynamic characteristics of synchronizer
variation with time of the voltage appearing across the synchronizer terminals when the camera synchronizer is
operated
3.7
ignition circuit
part of the photoflash unit provided to receive the signal from the synchronizer and fire the electronic flash tube or
flash bulb
4 Requirements
4.1 Polarities for synchronizer terminals and ignition circuit terminals
The polarities of the synchronizer terminals in a camera and that of the ignition circuit terminals in a photoflash unit
coupled with the camera are defined in 4.1.1 and 4.1.2. The polarity of the camera synchronizer terminals shall be
matched to that of the ignition circuit terminals in the coupled photoflash unit. When more than one photoflash unit
is connected to a single camera in parallel by use of a device such as an adapter, it is recommended that a reverse
current prevention circuit be incorporated in the adapter or the respective photoflash units to avoid an electrical
interference of one photoflash unit with another.
4.1.1 For the “camera accessory shoe with electrical contacts”, defined in ISO 518, and the “foot of photoflash
equipment with electrical contacts”, the contact P shown in Figure 1 shall be the positive pole, while the surface Q
shall be the negative pole and, when the photoflash unit is connected to the camera, the potential for P shall be
higher than that for Q.
4.1.2 For the “socket and plug in small flash connections for hand-held cameras” defined in ISO 519, the part P
shown in Figure 2 shall be the positive pole, while the part Q shall be the negative pole and, when the camera is
connected to photoflash unit, the potential for P shall be higher than that for Q.
4.2 Voltage across and current through synchronizer terminals and ignition circuit terminals
The voltage applied across the camera synchronizer terminals and that developed across the ignition circuit
terminals in the photoflash unit shall not exceed 24 V d.c.
NOTE The 24 V d.c. value is the same as the value of the “safety extra low voltage” specified in 8.1 in IEC 60335-1:2001.
The synchronization current flowing through the camera synchronizer terminals shall be 100 mA at maximum and
the current flowing through the ignition circuit terminals in any one of the photoflash units shall be 30 mA at
maximum.
2 © ISO 2002 – All rights reserved

a) Shoe b) Foot
Key
1 Part P
2 Part Q
3 Insulation
Figure 1 — Polarities for camera accessory shoe with electrical contacts
and foot of photoflash equipment with electrical contacts

a) Socket b) Plug
Key
1 Part P
2 Part Q
3 Insulation
Figure 2 — Polarities of sockets and plug in small flash connection for hand-held cameras
4.3 Ignition circuit operation
When a 4,4 MΩ resistor is connected across the ignition circuit terminals and a pulse voltage as shown in Figure 3
is applied across the terminals, the photoflash unit shall be fired.
NOTE 1 The resistance value of 4,4 MΩ is specified in consideration of the synchronizer leakage current and the cable
insulation resistance.
NOTE 2 See A.2 for the requirements for a photoflash unit having an ignition circuit which is equipped with precautions
against accidental firing and failure to fire due to noise or chattering of the synchronization contacts.

V is the voltage developed across ignition circuit terminals in a photoflash unit and is equal to 24 V d.c. maximum.
F
V is equal to 1,6 V.
SS
Figure 3 — Voltage waveform across ignition circuit terminals

4.4 Dynamic characteristics of synchronizer
When the camera is operated with a 24 V d.c. power supply and 240 Ω resistor connected across the camera
synchronizer terminals in series (see Figure 6) and the synchronizer has an electronic switch, then the terminal
voltage for the synchronizer shall be maintained at 1,5 V or less until the synchronization switch is turned off (see
the continuous thick line in Figure 4).
On the other hand, when the synchronizer has a mechanical switch, at least one of the time periods (T to T )
1 2
between the moment the synchronizer terminal voltage reaches 21 V and the moment a time of 150 µs elapses
and during which the voltage across the synchronizer terminals is maintained at a value of 1,5 V or less, shall be
10 µs or more (see the broken line in Figure 4).
NOTE 1 When the synchronizer has a mechanical synchronization switch, it is desirable that after a time of 150 µs elapses,
the synchronizer terminal voltage be maintained at 1,5 V or less over as long a time period as possible.
NOTE 2 It is desirable that the synchronization switch be opened after the shutter closing operation is started
4 © ISO 2002 – All rights reserved

4.5 Synchronizer leakage current
When a 24 V d.c. voltage is applied across the camera synchronizer terminals with the camera synchronization
switch turned off, the leakage current shall be 5 µA or less.
4.6 Electrical characteristics of cable
4.6.1 Cable resistance
When the cable is short-circuited at one end, the resistan
...