The housing of an implantable cardiac device is selectively made active or passive by an external connector member, such as a shorting plug or lead connector inserted in its header. Advantageously, the header, the shorting plug, and the lead connector all are constructed and arranged to conform to a pre-selected standard in the industry, such as IS-4. The header includes an access hole that is provided with several housing connector elements connected either to the conductive surface or to an internal electrical circuit. The external connector members each have a shaft with external conductor elements. Each shaft includes conductors such as wires. The housing is made active by inserting into the header an external connector element having two of its external connector elements connected by a shorting wire.