Siemens S7-300 Installation And Operating Manual page 142

Digital modules
8.6 SM 326; DO 10 x DC 24V/2A (6ES7326-2BF01-0AB0)
Redundant output signals
An output with series diode can be used for redundant control of an actuator. Redundant
control is supported for two different modules and without an external circuit. The two signal
modules must be connected to the same reference potential (M).
Note
Connect the SM 326; DO 10 x DC 24V/2A to the same load voltage for operation in
redundant mode. Install two redundant power supply units if a single power supply is
insufficient for reasons of availability. The power supply units must be coupled by means of
diode circuit.
Short-circuit to L+ at redundant interconnection
Prevent short circuits to L+ at the SM 326; DO 10 x DC 24V/2A with protected routing of the
signal lines.
The module may not be able shut down the actuator by switching off the corresponding
redundant output if a short-circuit to L+ is active.
Address assignment
Figure 8-40
142
WARNING
WARNING
Address assignment for SM 326; DO 10 x DC 24V/2A
Installation and Operating Manual, 01/2010, A5E00085586-10
Fail-safe signal modules