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LD Language Elements
SR2MAN01 11/2007 89
Discrete Inputs
Description The Discrete Inputs can be used exclusively as contacts in the program.
These contacts represent the status of the input for the smart relay connected to a
sensor (push button, switch, sensor, etc.).
The contact number corresponds to the number of terminals of the associated input:
1 to 9, then A to R (except for letters I, M and O) according to the smart relay and
the possible extension.
Use as a Contact This contact may use the direct state of the input (normally open mode) or its inverse
state (mode normally closed), see below.
Normally open mode:
Symbol of a normally open contact:
A normally open contact corresponds to the use of the direct state of the input. If the
input is supplied, the contact is said to be conducting.
Example:
Using a pushbutton to switch a lamp on and off.
If input 1 is supplied, contact I1 is closed, and coil Q1 is activated.
Normally closed mode:
Symbol of a normally closed contact:
A normally closed contact corresponds to the use of the reverse state (logical
complement of the direct state) of the input. If the input is supplied, the contact is
said to be non-conducting.
Example:
Controlling a lamp using an input in reverse state.
If input 1 is supplied, contact i1 is open, and coil Q1 is non-activated.
I -
I1 Q1
i -
i1 [Q1