Science fiction has, for the most part, taken for granted the existence of instant communication. Words and faces are conveyed across the universe without delay, and people light years apart have whole conversations without the awkward ten-second silence between sentences as the words are transmitted and received.
In modern times, communications delay is pervasive in our lives. Grainy reports from CNN correspondents continents away have already been infected. It took hours for commands to be received, executed, and confirmed by the Mars rover.
The cause of this delay is the speed of the radio waves on which data is carried. Through air, radio speak travels at the speed of light. While this might seem fast, the gap between the speaker and listener becomes more apparent as the distance increases from five thousand feet to five thousand miles.
In the technological timeline of OtherSpace, communications delay was eliminated somewhere around the middle of the twenty-second century when first contact with the Centaurans were made. During that time, Earth's scientific community experienced a golden age of knowledge and enlightenment. Thousands of theories were confirmed, from the simplest suppositions in chemistry to the most advanced particles in physics. It was at this time that the tachyon became significant.
The Centaurans had imparted a vital piece of information to the primitive humans: the theory (now law) of relativity cannot be broken. Nothing that exists within our spectrum of space-time can go faster than the speed of light.
But what's a law without loopholes. The tachyon is a subatomic particle that naturally went faster than the speed of light. That is, the law of special relativity did not apply to it, because it didn't exist within our space-time. When harnessed and transmitted in sequenced bursts, these tachyons can be used to convey a message to very distant stars without the dreaded delay.
The interstellar communications network soon rose. Because it took immense amounts of energy to trap free-floating tachyons and to fire them in a narrow cone, handhelds radios wouldn't suffice. Large space-based relay stations were needed, commonly referred to as data beacons, to direct the billions of messages sent to distant relatives per minute.
There are, on average, three data beacons for every populated solar system. These relay stations come in a variety of shapes of sizes and are usually public domain, maintained by the government. Some may be supported by smaller sector retransmitters for increased power.
The handheld commlink's communications range is limited to its own local system, as it does not transmit a signal strong enough to handle repeated retransmission across the datanet relays.
Destroying a solar system's beacons mean cutting off that system from the rest of the interstellar community. The relay stations' great value and great vulnerability make it one of the more important priorities of governments.
Special thanks to Gadget for this information; edits/updates on commlink range by Mika.