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IPROGRAMMING 
IDescription 
of 
internal devices 
I 
I 
Inputs 
x 
I 
Using inputs, communication is made between the PLC and external equipment via 
the  input  modules  off  the  PLC  system.  They  are  used 
to 
receive  ON/OFF 
commands and data from external devices such as  push buttons, select switches, 
digital switches etc..,  for use within the sequence program. 
Assuming that one  input point incorporates a virtual relay Xn  within the PLC, the 
normally open contact (NIO) and normally closed contact (NIC) of that input point 
can then be  used  in the program. There  is no  restriction 
to 
the  number 
of 
N/O 
contacts and N/C contacts used for that one input point. 
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/-;-a 
a 
I 
II 
I 
Input 
circuit (external devtces)  Sequence 
program 
I 
OUtDUtS 
Y 
I 
Like inputs, outputs enable communication between the PLC, via output modules in 
the PLC system, and external equipment.  Outputs provide program control results 
to 
external devices such  as  solenoids, magnetic switches, signal  lamps, digital 
indicators etc. 
Assuming that one output point incorporates a virtual relay coil Yn within the 
FLC. 
The N/O contacts and N/C contacts of this coil can also be used within the program, 
with no restriction on the number of times they are used. 
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