Siemens Simatic series Manual page 16

Resistor circuitry of the encoders
To detect a wire break, it is necessary that enough quiescent current is flowing even when
the encoder contacts are open. Connect a resistor of 25 kΩ to 45 kΩ with 0.25 W to the
encoder contacts for this reason.
Figure 3-2
Tip: Using the potential jumpers
Use the potential jumpers supplied with the front connector if you want to distribute the 24V
DC supply voltage to a neighboring module. This helps you to avoid having to terminate two
wires to one terminal.
Proceed as follows:
1. Connect the 24 V DC supply voltage to terminals 19 and 20.
2. Insert the potential jumpers between terminals 19 and 39 (L+) and between terminals 20
and 40 (M).
3. Use the terminals 39 and 40 to distribute the potential to the next module
Figure 3-3
Note
Ensure that the maximum current load of 8 A per potential jumper is not exceeded.
DI 16x24VDC HF Digital Input Module (6ES7521-1BH00-0AB0)
Manual, 08/2018, A5E03485952-AG
Resistor circuitry of the encoders
Using the potential jumpers
Wiring
15