Anti-defeat Double Bias Contact
The BMC-33B Anti-Defeat Magnetic Contacts are uniquely designed and constructed to make defeating almost impossible. The switch housing contains specially arranged reed switches. These reed switches are pre-set in a biased format with ring magnets, producing a symmetrical magnetic field. The magnetic layout is designed with a combination of three polarized magnets. This switch and magnetic combination produces a perfect symmetrical magnetic field in a balanced condition, as if no magnet field existed. Any attempt to bypass or defeat the BMC-33B with an external magnet will cause the magnetic fields to be imbalanced, thus causing an alarm condition.