An alien intelligence, after observing Voyagers trajectory to work out where it came from, would know that there is intelligent life on Earth.
How could they use that information to start communicating with us?
An alien intelligence, after observing Voyagers trajectory to work out where it came from, would know that there is intelligent life on Earth.
How could they use that information to start communicating with us?
The aliens wouldn't be able to use Voyager's systems directly - by the time it reaches them, they would have deteriorated beyond use, never mind even now we're near the limit of Voyager's antenna power capabilities - there's zero chance to hear it from a different system.
But the aliens should be able to reverse-engineer the system. They might find out what frequencies we use; on the off-chance scraps of memory of the computer are recoverable (likely by taking it apart atom by atom and performing statistical analysis on the memory cells to find traces of data that used to be there) they might even reverse-engineer the encodings.
Now, whether they'd be able to build a transmitter of power (or beam narrow enough) to reach the Solar System? We know for a fact, we can't - but that's likely a couple million years from now and we can't foresee advances in technology on such timescales. So they might use the information to build a system to send signal we'd be able to decode and understand. But no, using the actual electronics of Voyager as the radio would be completely implausible.
Never mind we keep making advances in space technology; it's likely by the time Voyagers cover 5% of the way to the next star systems, our newer probes will have long reached it, overtaking the old Voyagers, traveling at much higher speed... the only plausible alternative to that is that the aliens send the signal towards a dark, heavily irradiated, dead husk of Earth. The disks were very evocative, a wonderful publicity stunt, but Voyagers are simply too slow to get anywhere before either we get there by other means, or destroy ourselves.