HD Radio technology allows participating broadcasters to provide you with a higher fidelity digital AM and FM signal. Additionally, HD Radio stations often offer additional channels of content that is not available on the standard FM broadcast.

The digital signal is broadcast using a proprietary audio compression codec called HDC (High-Definition Coding). Current FCC rules also require stations to simulcast the same audio signal in analog as well, so if the primary digital signal is lost, the HD Radio receiver will revert to the analog signal, thereby proving seamless operation.

For HD AM broadcasts, the stations can choose broadcast rates between 40-60kbps, with most stations using the 40kbps as this method is more robust and less likely to cause dropouts due to signal strength issues. In theory the increased bandwidth on the AM band allows for AM radio at FM radio quality.

The FM HD broadcasts allow options to carry 100, 112, 125 or 150kbps of data when simulcasting with an analog signal. The system also has the capability of several pure digital modes up to 300kbps, however at the moment this would require a change to the current FCC ruling requiring the station to simulcast the signal in analog before stations can broadcast in pure digital.

FM stations also have the option to subdivide the digital audio streams into sub-channels (i.e. 87.5 HD1, HD2, etc.), which is often done to allow for more variety from one station. Each individual sub-channel can have its own audio quality from CD-quality (100kbps), FM-quality (25-50kbps), AM-quality (12kbps), or Talk-quality (5kbps).

For full information and to find stations in your area with HD please visit http://www.hdradio.com.

Input bussing allows the signal from one input to be bussed across to other inputs without requiring multiple input connections. This feature is often used in multichannel custom installation amplifiers. It reduces the cost of multiple cables and time during installation.

Some tuners/receivers come equipped to display RDS (sometimes called RBDS or Radio Broadcast Data System), which is a text display, usually in the form of a song title, artist name, station call letters, or format. More adventurous information might include a scrolling message saying "be caller number 10 now and win $100!". RDS is widely used in Europe, where it was introduced in 1987 (It didn't debut in the U.S. until 1993). Not all stations use RDS, and those that do may not offer full RDS service. In addition, the functions may not work properly during poor reception. RDS features ordinarily include RDS search, format search (PTY), traffic announcement search (TA), emergency program reception, alternate frequency (AF), and automatic clock adjustment (CT).