A - 1  A - 1 
• SAFETY PRECAUTIONS • 
(Read these precautions before using this product.) 
 
Before using this product, please read this manual and the relevant manuals carefully and pay full 
attention to safety to handle the product correctly. 
The instructions given in this manual are concerned with this product. For the safety instructions of the 
programmable controller system, please read the CPU module user's manual. 
In this manual, the safety precautions are classified into to levels: " WARNING" and " CAUTION". 
 
Under some circumstances, failure to observe the precautions given under " CAUTION" may lead to 
serious consequences. 
Observe the precautions of both levels because they are important for personal and system safety. 
Make sure that the end users read this manual and then keep the manual in a safe place for future 
reference. 
 
[Design Precautions] 
 
WARNING 
• For operating status of each communication failure, refer to this manual. Incorrect output or 
malfunction due to a communication failure may result in an accident. 
• If a coaxial cable is disconnected, this may destabilize the line, and a network communication 
error may occur in multiple stations. Provide an interlock circuit in the sequence program so that 
the system will operate safely even if the above error occurs.    Failure to do so may result in an 
accident due to incorrect output or malfunction. 
• When changing data of the running programmable controller from a peripheral connected to the 
CPU module or from a personal computer connected to an intelligent function module or special 
function module, configure an interlock circuit in the sequence program to ensure that the entire 
system will always operate safely. 
For program modification and operating status change, read relevant manuals carefully and 
ensure the safety before operation. 
Especially, in the case of a control from an external device to a remote programmable controller, 
immediate action cannot be taken for a problem on the programmable controller due to a 
communication failure.   
To prevent this, configure an interlock circuit in the sequence program, and determine corrective 
actions to be taken between the external device and CPU module in case of a communication 
failure. 
 
 
! !
!
!