A subspace transceiver, also known as a subspace comm, subspace radio, hypertransceiver, subspace vox, or wide-band radio receptor, was a standard device used for instantaneous, faster-than-light communications between nearby systems. Similar to its shorter-ranged cousin, the comlink, subspace transceivers relied on energy to broadcast signals. Starships carried these units to broadcast distress signals and other important messages. They used subspace as the communications medium. The subspace transceiver of an Imperial Star Destroyer had a range of 100 light-years.
A comm slicker using a ship's subspace radio
Many planetary governments, large corporations, and wealthy individuals maintained private subspace transceivers. Because each radio had a range of up to several light years, governments used these units to connect local planets with a sector-wide communications grid. Although much more powerful than standard comlinks, subspace radios were not nearly as advanced or effective as the HoloNet. Most planets were integrated into local subspace networks that used transceivers aboard deep-space satellites to link dozens of worlds in an instantaneous and continuous flow of data. These networks normally handled news, sports, entertainment, and educational programming. Individuals and corporations purchased broadcast time for private messages, with fees running anywhere from one to twenty credits per ten seconds of transmission time.
Hundreds of subspace networks were scattered across the galaxy, so a message could theoretically be sent across the galaxy by bouncing it across multiple networks. While this process was much more affordable than the HoloNet, messages could be delayed for hours or days as they were routed through different networks. Because each network had different communication protocols, messages could be corrupted or lost, and so it was often cheaper and safer to send long-distance messages by courier ships.
Subspace radios are the primary form of communication on Star Trek.