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Operating Instructions
ISD 230/260/280 IR Data Transmission Systems
Chapter
3
© SICK AG · Auto Ident · Germany · All rights reserved
8 008 207/30-11-2001
14
Product description
3.2
Method of operation
The ISD systems each comprise two units with different carrier frequencies. Each of the
components contains an optical data transmitter and receiver as well as a bidirectional,
electrical data interface (
Fig. 3-2
).
Fig.
3-2: Block diagram: operating principle of the ISD system
With one pair of devices, data can be transmitter and received simultaneously, i.e. data
transfer is possible in both directions. Different carrier frequencies prevent mutual optical
interference.
The data levels pending at the electrical interface of a transmitter (input) are transferred
optically to the opposite station using the FSK modulation method. The receivers on the
other side then reconvert the optical signals to electrical data levels and output them via
the electrical data interface (output).
If you are using the RS 485 interface, both units are ready to receive (RR) in the idle
state. The station which first receives data on the electrical interface determines the
direction of transmission until the data string has been transmitted. Both stations are
ready to receive again once transmission has been completed (automatic direction
switching). The data transfer rate must only be set on the ISD if you are using the
RS 485 interface.
The light path between the two units is monitored constantly. An LED on the front of each
unit signals interruptions in the light path and inadequate reception conditions. A
switching output, which is active when the light path is unobstructed (free), is provided in
addition to the LED.
Each of the device units in the ISD 230 system is also equipped with a switching output
which is deactivated under poor transmission conditions (e.g. lenses contaminated). The
transmitter on every unit can be deactivated via a switching input.
Electrical
Interface
Electrical
Interface
Distance:
0.2 ... 150/180/200 m
Light path
Station 1
Station 2
Transmitter
Receiver
Transmitter
Receiver