Siemens S5-135U/155U System Manual page 418

Analog Input/Output Modules
Enable Input
The enable circuit requires an external 24 V voltage at enable inputs F+/F- in
the front connector. If there is no voltage at F+/F-, the modules will not
acknowledge.
When the front connector is swivelled away from the front strip of the
module, the supply of power to the enable input is interrupted, i.e. the
module is switched off and can no longer be addressed by the user program: a
timeout (QVZ) occurs in the CC.
Switching off the
The -4Ux12 type modules additionally offer the facility for changing the
Enable Input
enable mode. The modules have a jumper accessible from above in the
vicinity of the addressing switch.
Figure 9-13
Jumper inserted:
Jumper open:
Examples of functioning of the enable inputs:
9-36
Enable Jumper
Enable Input and Enable Jumper
Enable input (F+/F-) active (factory setting)
Enable input (F+/F-) switched off
To switch off individual subprocesses, i.e. outputs of various modules can
be operated from a common load supply and yet activated separately.
The load voltage of individual modules can be monitored without
additional circuitry. Any reactions to failure of the load voltage can be
programmed in the QVZ (timeout) organization block.
System Manual
C79000-G8576-C199-06