Digital modules 
  8.5 SM 326; DO 8 x DC 24V/2A PM 
Fail-safe signal modules 
Installation and Operating Manual, 01/2010, A5E00085586-10 
133 
Prevention/control of cross circuits between the P and M switches 
To control cross circuits between P and M switches of a fail-safe digital output, we 
recommend the following wiring variant: 
/
0
/
0
'2[3
'2[0
60
'2['&9$30
 
Figure 8-39  Wiring scheme 2 relays at digital output of SM 326; DO 8 x DC 24V/2A PM - Controlling 
cross circuits 
 
 
Note 
The module only detects a "wire break“ fault at the P or M switch of its output if the both 
relays are wired separately to the P or M switches. 
Assignable parameters for applications 1 and 2 
Table 8- 16  Parameters of the SM 326; DO 8 x DC 24V/2A PM for applications 1 and 2 
Parameters   Range of values   Type  Effective range 
"Parameters" tab 
F parameter: 
F monitoring time  10 ms to 10000 ms  Static  Module 
Module parameters: 
Diagnostic interrupt   Activated/deactivated  Static  Module 
For single channels or channel pairs: 
Activated  Activated/deactivated  Static  Channel 
Diagnostics: Wire break  Activated/deactivated  Static  Channel 
8.5.4  Diagnostic messages of SM 326; DO 8 x DC 24V/2A PM 
Diagnostics using the LED display 
The F-SM indicates faults by means of its SF LED (group fault LED). The SF LED is 
activated when the F-SM generates a diagnostic message.  
The SF LED flashes as long as a cleared fault has not been acknowledged. It goes dark 
when all faults have been eliminated and acknowledged. 
The SF LED flashes until you acknowledge passivation following a module fault.