Filtered connectors are designed to protect electronic equipment or systems from unwanted radio-frequency interference (RFI) or electromagnetic interference (EMI). Filtered connectors can also be equipped with transient voltage suppression diodes to protect equipment from an electromagnetic pulse (EMP) that might occur from a power surge, like during a lightning strike.
Filtering is generally found on just one side of a mated pair and is traditionally the receptacle side. All filtered connectors mate with a corresponding connector that has the same insert arrangement and opposite contact gender. There are several filtering options including C filters (pure capacitive filter), CL-LC filters (combined inductance and capacitance filtering), and Pi filters (capacitive and inductive filtering). Type of filtered connectors include chip capacitor, discoidal capacitor, planar array, Pi with planar arrays, and Pi tubes.