Siemens SIMATIC NET PROFIBUS User Manual

3-2

PROFIBUS Optical Bus Terminal (OBT)

C79000-G8976-C122-02

The OBT supports all PROFIBUS transmission rates (12 Mbps , 6 Mbps, 3 Mbps,
1.5 Mbps, 500 Kbps and 187.5 Kbps, 93.75 Kbps, 45.45 Kbps, 19.2 Kbps, 9.6
Kbps).

The transmission rate is detected automatically. No settings are necessary.

The OBT supports the fiber types listed in the table below:

Table 3-1

Distance Covered by Fiber-optic Cable between Two Devices on the Optical
PROFIBUS DP 

Fiber Type

Distance Between Two Devices

Plastic FO 980/1000 

µ

m with 2 fibers

and max. 200 dB/km cable attenuation

0.1 m to 50 m

PCF FO 200/230 

µ

m with 2 fibers and

max. 10 dB/km cable attenuation

0 m to 300 m

The specified distances between the devices assume that the partner devices use
the same optical components as the OBT. This is, for example, the case with the
IM 153-2 FO, IM 467 FO and OLM 12M.

The transmission rate is independent of the type of fiber used and the cable length.
It can be up to 12 Mbps.

The following accessories are available:

S

Plastic FO cable (sold in meters), connectors, polishing set and tools for
connectoring plastic FO cables
The plastic fiber-optic cables are supplied with connectors. The plastic simplex
connectors can be fitted with the available tools on site.

S

PCF FO cable (with connectors)
PCF cables in fixed lengths are available with 4 simplex connectors already
fitted.

The OBT has 4 LEDs for displaying the various states.