Siemens S7-300 Installation And Operating Manual page 172

Digital modules
8.7 SM 326; F-DO 10 x DC 24V/2A PP (6ES7326-2BF10-0AB0)
Wiring scheme of application 6
Each process signal requires one actuator which is controlled redundantly by the two digital
modules. The load voltage supply is wired to terminals 2L+/2M, 3L+/3M of the digital module.
Figure 8-60
Note
Use the same reference potential for both modules.
172
Wiring scheme of the SM 326; F-DO 10 x DC 24V/2A PP for application 6
Installation and Operating Manual, 01/2010, A5E00085586-10
Fail-safe signal modules