Current adaptor for car radio telephones

摘要

The adaptor (10) includes the current connector (11) that plugs into the cigar lighter to provide electric current. The adaptor has the radio frequency input (16) for signals from the external antenna of the radio telephone. The current and RF signals both pass down a wire (12) to the radio telephone input connector (14). A switch formed with the current connector allows selection of the antenna. The connector includes a resistance between a connector and ground which drives the node towards a predetermined value required to activate the switch.