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46
Configuring the short range fibre optical
modem
The module can also synchronise received data with the send clock. This is not normal-
ly necessary in this application. Synchronisation ON/OFF is controlled by switch 2,
which shall normally be set in OFF position. When the module is set for synchronisa-
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.
Note!
After any change of settings, the modem has to be reset by the Reset button located be-
low the DIP-switch.
Table 2: Setting of timing signal
Switch no.
Function
3
4
OFF
OFF
Timing created by the modem
OFF
ON
Timing recovered from received optical signal
ON
OFF
Timing created by the differential function
ON
ON
No timing, the data transmission will not work
There are also some jumpers on the circuit board that has to be correctly set. One, S4
according to figure 10, is for changing the functionality between article number
1MRK 001 370-BA (marked 1MRK001471-BA) and 1MRK 001 370-DA (marked
1MRK001471-DA). The difference between these two is that the signal is inverted in
one compared to the other.
The other jumper is S3 that has to be in bottom position, as marked in figure 10. If it is
in top position the communication will not work. (In top position the transmit clock is
supposed to be created in the CPU on the MPM module which is not possible). On
JTAG/ISP there shall be no jumpers inserted.
Note!
For a homogenous system, that is when the set up are identical at both terminals, the
article number does not matter. When using a set up according to figure 9 only at one
end and for example a direct G.703 connection at the other end a short range fibre op-
tical modem according to 1MRK 001 370-DA must be used. Using a short range fibre
optical modem according to 1MRK 001 370-BA will not work.
Chapter 8
Configuring the digital
communication modules
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