Mitsubishi Electric MELSEC-Q Series User Manual page 54

(8) Measures against static electricity
When using an insulation displacement connector without
connector cover, a connected cable for the connector is thin in
applicable wire size and coating. Therefore, note that the module
may cause an electric discharge failure.
As measures against the failure, using pressure-displacement type
connector whose applicable wire size is thick or soldering type
connector is recommended.
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