Tape switch's controller has both 4-wire and 2-wire detection function.
Circuit diagram and connection example

• Steady state
   Constant current (I) flows and relay K1 is in the excited state    [safety output ON]
• Voltage drop (power loss)
    Current (I) does not flow and K1 is in non-excitation state [Safety Output Off]
• Sensor works
    Relay coil K1 has short-circuit non-excited state [Safety output off]
• Sensor is defective
   (open disconnection switch conductor defective,  lead wire disconnection)
    Current (I) does not flow and K1 is in non-excitation state [Safety Output Off]

Safety output off → Stop the machine to operate the emergency stop circuit
Since both 4-wire and 2-wire type are equipped with disconnection detection function,The machine can be stopped.