RDS EON and travel services in BBC radio networks

The alternative frequency (AF) feature of RDS provides the means whereby a single tuner RDS receiver can emulate the performance of a dual-tuner model. By providing the receiver with a list of frequencies that are declared to be genuine alternatives to the tuned frequency in any given area, the receiver may use a simple (and very rapid) check of signal strength to determine the eligibility of candidate frequencies, and then determine whether to switch. RDS EON (Enhanced Other Networks)provides the means by which one programme service may distribute frequency information about other services. Each transmitter, as well as carrying an AF list for its own service tailored to the specific area, is able to carry AF lists for other services which are receivable in its coverage area. An EON receiver is then able to update the relevant frequency stores in its memory and ensure that any switches are made in the shortest possible time. The BBC has incorporated traffic and travel bulletins into the programme output of its local and national radio stations. Through the RDS system the BBC now flags over four thousand separate bulletins each and every week, made available to network radio listeners by the EON feature of the system.