A filter connector is disclosed for reducing electro-magnetic interference. The connector may be in the form of an adaptor which is mounted between mating plug and receptacle members of electrical connectors, such as the type utilized in the telephone industry. The adaptor comprises a monolithic ceramic capacitor mounted between the termination ends of plug and receptacle connector members, with the edges of the capacitor disposed between the two rows of contacts in the connector members. The capacitor has a plurality of parallel, spaced live electrodes on its opposite faces engaging the contacts in the connector members. At least one ground plane is embedded in the ceramic substrate of the capacitor, and is coupled to the housing of the connector members. Other connector and capacitor circuit configurations are disclosed.