Introduction
PROFIBUS Optical Bus Terminal (OBT)
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Operating Instructions, 04/2016, C79000-G8976-C122-07
Connections
The connection between the individual bus nodes takes the form of an optical bus with two-
fiber plastic fiber-optic cables (plastic fiber-optic cables are also known as POF, Polymer
Optical Fiber) or PCF fiber-optic cables (PCF = Polymer Cladded Fiber, synonymous with
HCS1 fiber-optic cable). Since fiber-optic cables (FO cable) are completely insensitive to
EMC interference, complex grounding concepts and protection measures are unnecessary.
This also applies to the laying of a equipotential bonding cables. Due to be opto-electronic
conversion, there is automatically electrical isolation so that potential differences as can
occur in extensive plants are no longer noticed.
1) HCS is a registered trademark of Spectran Speciality Optics and stands for "Hard Polymer
Cladded Silica Fiber".
Sensitivity
Just as the FO cable is insensitive to EMC interference, an FO cable also emits no
electromagnetic waves into its environment. Sensitive electronic devices located in the
vicinity of the fiber-optic cable therefore need no additional protection or suppression
measures.
Power supply
The OBT requires an operating power supply of 24 VDC that is connected via two screw
terminals.
Operating state
LEDs signal the current operating state and any problems affecting operation.
Mechanical construction
The mechanical construction consists of a compact plastic housing that can be mounted
either on a DIN rail or any flat surface.
