Siemens SIMATIC STEP 7 V5.2 Getting Started page 27

Symbols are indicated in red if, for example, they do not exist in the symbol table, or if
there is a syntax error.
STEP 7 Getting Started
A5E00171228-01
Creating a Program in OB1
Click the ??.? sign and enter the
symbolic name "Key_1" (in quotation
marks). Alternatively, you can select
the name from the displayed pull-down
list.
Confirm with Enter.
Enter the symbolic name "Key_2" for
the second normally open contact.
Enter the name "Green_Light" for the
coil.
You have now programmed a
complete series circuit.
Save the block if there are no more
symbols shown in red.
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