an accident, while reactive PD are those that contain the energy
released by this interaction after it has happened.
Another well-known classification of PD, proposed by Shingo
[5], concerns the one that differentiates a control function from
a warning function. The control function requires there to be one
or more of the following features: (a) it turns off the machine, or
physically blocks the continuity of a manual process, once it detects
the abnormality; (b) it does not allow the operator to choose how
to carry out the task, but obligates him to perform it correctly;
(c) it automatically excludes defective parts from the production
flow. The warning function means that the poka-yoke signals, by
means of symbolic devices (e.g. lights and/or audible alarm), the
occurrence of the abnormality [5].