Siemens S7-300 Installation And Operating Manual page 107

Sensors supported
The following illustration shows the supported sensors and their connection to the SM 326;
DI 8 x NAMUR.
NAMUR sensor monitoring for
 Wire break
 Short-circuit
Wiring and block diagram
The following figure shows the the wiring and block diagram of SM 326; DI 8 x NAMUR.
Figure 8-24
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
Wiring and block diagram of SM 326; DI 8 x NAMUR
8.4 SM 326; DI 8 x NAMUR
Connected contact monitored for
 Wire break
 Short-circuit
(resistors installed directly at the contact)
Digital modules
107