|Standard d-sub connectors can not guarantee protection from EMI/RFI, even when enclosed in shielded hoods. Filter d connectors and adaptors are an ideal solution to reduce or eliminate EMI.
A filtered connector is widely recognized as the most effective point to filter noise either entering or exiting an EMI enclosure. Noise induced on a signal line within the box can be stripped off as it passes through the shielding enclosure, preventing radiation to adjacent equipment. Filtered connectors are also used to provide system immunity from external noise sources.
Many different configurations of filters have been developed to address a variety of circuit requirements. The simplest design is the C or feed-through filter which consists of a single capacitor inserted between the signal line and ground. As the conducted signal frequency increases, the effective resistance of the capacitor decreases, and therefore shunting higher frequencies to ground.