Wiring the S7-400
4-12 AutomationSystem S7-400 Hardwareand Installation
A5E00850741-01
4.8 Parallel Wiring of Digital S7-400 Outputs

Parallel Wiring of a Digital Output with Different Rated Load Voltages

The parallel wiring of a digital output (rated load voltage 1L+) with another digital
output (rated load voltage 2L+) or a rated load voltage 3L+ is only possible using
series diodes.
1L+ 2L+ 3L+
Figure 4-5 Parallel Wiring of a Digital Output with Different Rated Load Voltages

Parallel Wiring of a Digital Output with Identical Rated Load Voltages

If the L+ supplies of the digital output modules and the L+ voltage connected in
parallel to the output are always the same (difference < 0.5 V), there is no need to
use diodes, see figure 4-6.
L+
Figure 4-6 Parallel Wiring of a Digital Output with Identical Rated Load Voltages