Brochure/Catalogue

Glossary
Device categories The device category determines which equipment can be used in which
zone. There are six device categories. The categories 1 G, 2 G and 3 G are
classications for gas explosion protection (G = Gas). Equipment with 1 G is
suitable for zones 0, 1 and 2. Equipment with 2 G is suitable for zones 1 and 2.
Equipment with 3 G is suitable for zone 2. The categories 1 D, 2 D and 3 D are
classications for dust explosion protection (D = Dust). Equipment with 1 D is
suitable for zones 20, 21 and 22. Equipment with 2 D is suitable for zones 21
and 22. Equipment with 3 D is suitable for zone 22.
Device groups Equipment is divided into groups I and II. Group I concerns underground mining
while group II concerns explosion protection for gas and dust in all other
applications.
DTM DTMs (Device Type Manager) are software drivers that are vendor- and device-
neutral. DTMs dene functions for access to device parameters, troubleshooting,
conguration and operation of devices The DTM species all device-specic
information, functions and rules (such as the device structure, communication
capabilities, internal dependencies and the human-machine interface (HMI)).
Device manufacturers make available a Device Type Manager (DTM) software
driver for each device or device group.
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EIA-232/ RS232 The term EIA-232 (originally RS232) refers to a serial interface standard
developed by a U.S. standards committee (now known as the EIA –
Electronic Industries Alliance) in the early 1960s. EIA-232 species the
connection between the data terminal equipment (DTE) and the modem
(data communication equipment or DCE). It denes timing, voltage level, plug
and protocol details. EIA-232 denes a voltage interface. The information
bits are encoded using electrical voltage. The data lines (TxD and RxD) use a
negative logic whereby a voltage level between -3 V and -15 V (ANSI/EIA/TIA-
232-F-1997) represents a logical one and a voltage level between +3 V and +15
V represents a logical zero. Signal levels between -3 V and +3 V are undened.
EIA-422/ RS422
EIA-422 (also known as RS422) is an interface standard for cable-based
differential, serial data transmission. In contrast to the asymmetric serial
interface specied by the EIA-232 standard, the EIA-422 interface is designed
for symmetric transmissions. This means that two sets of twisted pair wires are
required to carry the positive and negative signals from the sender to the receiver.
This minimises common-mode interferences and also increases the data rates
in comparison to the asymmetric EIA-232 interface. EIA-422 can be used to
establish a full-duplex, point-to-point connection. Multi-drop networks with one
sender and up to ten receivers are also possible. The sender and receiver in multi-
drop networks can only be operated in half-duplex (in one direction). Because of
the high data rate (up to several MBit/s), a wire pair on the EIA-422 interface must
be terminated with a terminating resistor (normally 120 ohm).
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Technical appendix/Glossary
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