The two element antenna that you see on the back of newer 740 cars is for the CPT8000. It installs with double sided tape at rear of roofline and the antenna wire is fed under the rubber liner that surrounds the rear window and feeds through a predrilled hole in your trunk (pop your trunk if you have a 98 or newer 740 and you'll see the black rubber plug near the lower left corner of the base of the rear window) This antenna wire connects to its mate antenna wire that is part of the red DB25 connector you asked about (trace the separate wire from that connector and you'll find a black plastic capped antenna mini coax connector under the fabric tape).