Inductive type proximity switch with NPN (Normally Open) transistor switch LJ12A3-4-Z/BY. Output upon detection. 

• Diameter of Head : 10.5mm/ 0.42"
• Detecting Distance : 4mm/ 0.16";
  Work Voltage : DC 6-36V;
  Consumption Corrent : Max 200mA
• Size : 5.8 x 1.2cm/ 2.3" x 0.5"(L*Max.D);Cable Length(Approx.) : 115cm/ 45.3";
  External Material : Plastic, Metal
  
  Wire
• Brown: Positive Power
• Blue: Negative
• Black: NPN output