Electronic or Electro-mechanical devices change state depending of the presence or the absence of the yarn, the yarn sensor is the most sensitive protection for the spinning machines. During the yarn processing, the sensor purpose is to immediately and automatically detect the breakage or stoppage of one or more yarns. The sensor will give the operator on duty an alarm with a visible LED flashing signal. It will simultaneously send out an electrical signal to the yarn cutter to cut off the broken yarn and grip the cut end, or send a digital signal to the PLC.