Siebert SX102 Série Manuel D'utilisation page 42

Application example D
Data lines RS485
To achieve the highest possible interference immunity, the data lines of the RS485
have to be terminated on both ends. The required resistors are provided in the unit
and can be connected on the screw terminal strip with a jumper (see block diagram,
terminals ZR, ZT).
The polarization of the data lines must be ensured by means of the master.
For the data lines, you always have to ensure that:
Shielded twisted-pair cables of sufficiently large cross-section are used.
The shielding is to be connected at both line ends.
For the signal ground (GND), a wire pair short-circuited on both ends is used in
the data line. The shielding may not be used as the signal ground.
A twisted core pair is used each for Tx+ and Tx- and for Rx+ and Rx-. Non-
observance of this instruction causes the protective function of the twisted-pair
cable to be lost!
Improperly terminated data lines cause faults during data transfer.
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Setting in menu item 1: RS485.2
Setting in menu item 6: ACK/NAK (recommended)
BAL SX102 SER M 1.10