Label Sensors allow the labeling machine to "see" each label.  The standard label sensor will read a gap in between each label to tell the machine when to begin or stop feeding a label.  The label sensors allow the labeling machines to supply one label for each container passing through or placed in the machine.

Certain labels, such as clear labels, may require special sensors when the backing paper or gap cannot be diffentiated from the label itself.  In rare cases, for unusual labels, label manufacturers may include a dot or other readable symbol, known as an "eye-mark" for the label sensors to read.  The correct label sensor for your labeling machine will be determined by the type of label you are using!