ABB REL 551 2.3 Series Installation And Comissioning Manual page 56

50
Configuring the short range fibre optical
modem
The module can also synchronize received data with the send clock. This is not normal-
ly necessary in this application. Synchronization ON/OFF is controlled by switch 2,
which shall normally be set in OFF position. When the module is set for synchroniza-
tion (switch 2 = ON) switch 1 must be set in the position corresponding to the Sync LED
that is brightest. If both have the same brightness the switch can be set in any position.
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OFF OFF Timing created by the modem
OFF ON Timing recovered from received optical signal
ON OFF Timing created by the MPM module
ON ON No timing, the data transmission will not work
There are also some jumpers on the circuit board that have to be correctly set. One, S4
according to figure 13, is for changing the functionality between article number
1MRK 001 370-BA delivered with version 1.1, 1.2 and 2.0.(marked 1MRK001471-
BA) and 1MRK 001 370-DA delivered with version 2.3 and higher (marked
1MRK001471-DA). The difference between these two is that the transmitted and re-
ceived signal is inverted in one compared to the other.
When a terminal of version 1.1, 1.2 or 2.0 is to communicate with a terminal of version
2.3 or higher it is necessary that the jumper is changed to 1 MRK 001 370-BA in the
version 2.3 terminal. This is due to that older versions of this module lacks the possibil-
ity to set article number, they are fixed set at 1 MRK 001 370-BA. If both terminals
however include modules with possibility to change article number it actually doesn't
matter what article number is used as long as the same number is used in both terminals.
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