Information is the glue that holds interstellar civilizations together. It is what allows far flung worlds to remain in touch with each other, what allows cultures and languages to remain homogenous enough to not diverge so much as to become alien in a few generations time. Information is vital for technological progress and for defense. The means by which information travels around known space is largely familiar to a visitor from the 21st century...radio is still commonly used...but there is also the innovation of faster than light communications that has revolutionized the way that people keep in touch across the stars.
The average citizen, whether Confed, Selven, or Talesian, usually has in his possession a personal communications device..called a comm. Comms can take the form of a compact cell phone, a wrist watch, an earbud, a cranial implant, or any number of other forms, based upon the user's needs or preferences. They function like 21st century cell phones, transmitting and receiving radio waves to a nearby transponder that in turn retransmits the signal through wires or through satellite, then back to another transponder and to the recipient. Comm signals can cover several kilometers distance before they require a transponder to boost the signal. Comm devices use radio waves and thus are limited to the speed of light, unless they make use of an FTL transponder, covered below.
Personal comm devices are powered either by compact batteries or by tiny fuel cells, giving them many days of operation before they have to be recharged. They are generally inexpensive and not difficult to replace.
Phone numbers are a more complicated thing in the 24th century, with populations measured in the hundreds of billions scattered across hundreds of planets, moons, asteroids, space stations, and starships. How this typically works is that every individual has a unique alphanumeric ID code that serves as his personal phone number and email address, that ID code following him wherever he goes. This is called a Mobile ID Address, or a MIDAs. Interstellar monitoring networks track the movements of each MIDAs, routing signals to wherever it happens to be at the moment.
Some people don't want to be tracked wherever they go. Whether due to profession or paranoia, or perhaps having been born on a world where MIDAs are not assigned at birth. Instead they rely upon a communications registry system (the Interstellar Communications Registry, ISCR, or ISCaR) that assigns an alphanumeric code broken down by system, planet, country, state, city, neighborhood. For example, a residential ISCaR number in Seattle, Washington might look something like this: SOL-3-PANW-SEA-CWF-406-2624. Modern communications terminals usually feature an intuitive touch display that makes entering ISCaR numbers fairly easy.
For people who don't want to rely on a MIDaS-based comm device, there are public comm terminals available nearly anywhere. It is also quite easy to purchase a disposable comm device that is difficult or impossible to trace, allowing for quick, anonymous communication.
Communications on a larger scale across a planet are made possible by a network of fiberoptic cables, high-powered radio transmitters, and satellite relays, allowing near-instant communication to anyplace on a planet or in its orbital vicinity. Most civilized planets have virtually no dead zones when it comes to communications. Less sophisticated colony worlds usually have dead zones over less developed regions.
Most vehicles, ranging from ground cars to aircraft, contain radios that tie them into the planetary network, aiding them in navigation and providing access to any data desired.
Communications between the planets of a stellar system is typically accomplished by a network of powerful relays that broadcast a tight beam of radio between each other. Very high density data signals tend to utilize x-rays since much more information can be carried by the much higher energy photons. Signals transmitted across interplanetary relays can take anywhere from minutes to hours to travel through a stellar system, so a certain delay in signals is expected. Live communications are only practical between locations that are within a few light minutes of each other, otherwise messages are recorded, stored, and then transmitted all at once.
Interplanetary transponders also serve the role of navigational beacons, guiding spacecraft along safe flight paths through the system.
Starships also use high energy transmitters similar to the power levels used for interplanetary communications. Narrow band, high energy transmissions between starships are common for sending large volumes of data, while broader, lower energy signals can convey simpler messages, usually text or audio.
FTL communications, covered in more detail below, can also be used within a star system across distances of several AU, though such signals have far greater energy requirements and are usually reserved for emergencies (on the civilian level) or for millitary communications.
Considering the vast distance between stars, radio communications is highly impractical. Even if the sheer wait isn't bad enough (over four years to send a signal from Earth to Arua), the average signal used for interplanetary communications will spread out and weaken to such an extent that it would be virtually undetectable by the time it reaches its destination.
In the early days of slower-than-light interstellar travel, massive transmitters were built that utilized tightly focused laser beams to transmit signals with enough energy to be detectable from a neighboring star system. This system got some limited use until the discovery of hyperspace travel completely changed the nature of interstellar travel and communications.
No sooner than scientists figured out how to build a functioning warp drive, they also figured out a means of transmitting information through the medium of hyperspace. Hyperspace communications is a stranger business than using radio, as signals transmitted through the hyperspace medium do not always travel at the same speed. Similar with the "phase displacement" states of Warp travel, there are also "phase displacement" states in hyperspace communication. Low phase displacement results in a signal that travels slower but requires less energy to transmit or receive, while a high phase displacement results in a signal that is much faster and also requires much more energy to transmit or receive.
Hyperspace Data Transmission, also known as HyperTrans, HyperDat or HyperRadio, is the means of communicationg across interstellar distances used by all factions in the known universe. Its variable levels of speed and power results in a fairly complex network of transponders that service known space, called the HyperNet. Low energy transmitters link neighboring star systems with only seconds of delay, while high energy boosters send signals across hundreds of light years distance with little more than minutes of delay. Most civilians can make use of the HyperNet at a reasonable cost, making due with interstellar communication with some minor delay, though faster communications are purchasable for a higher cost.
HyperTrans is a costly service to use because of its energy requirements. To send and receive signals a HyperTrans must have a substantial source of energy to draw upon at all times. The power demands of these devices prevent them from being smaller than units that can be installed in single-seater spacecraft.
Another function of the HyperNet is that it provides a series of beacons for starships to follow on the interstellar level, which is essential for safe navigation. All starships capable of Warp travel will have HyperTrans, at least of sufficient strength to communicate with neighboring systems....enough to contact the nearest HyperNet transponder. Military starships will have much more powerful HyperTrans, allowing them to communicate across hundreds of light years distance with little delay. HyperRadios will function for ships in Warp as well as in normal space, though signals in Warp may be distorted or delayed more than in normal space, usually meaning that signals sent or received while in Warp are simpler in content.