Alternative frequency (or AF) is an option that allows a receiver to re-tune to a different
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
that provides the same station, when the first
radio signal becomes too weak (e.g. when moving out of range). This is often used in car
stereo system
Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
s, enabled by
Radio Data System
Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM broadcasting, FM radio broadcasts. RDS standardizes several types of information transmitted, including time, sta ...
(RDS), or the
U.S.
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous ...
-based
Radio Broadcast Data System (
RBDS
Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identificat ...
).
References
Radio technology
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