The other day I mentioned Sailing the Sea of OSINT. Then in a Facebook group I’m in, they posted the BBC article about Ambulances Jamming car radios. In the group we made some speculations. But having a bit of a radio background, HAM Radio, CB Radio, and Broadcast Radio in college. I know how some of systems work.

So I went and dug up several articles on their pilot program. None however said how they worked. Just that they worked with the RDS radios in some cars. So I went and looked up RDS. Radio Data Systems, and the similar Radio Broadcast Data Systems in North America, is a protocol for sending data over the airwaves along with an FM signal.

In this case of both, they use PTY tags to associate what the data is. This is the same system that displays  the radio system call sign and song title on some radios. It can do more like say what type of music station it is based off the tags they use. This would allow people to search by genre.

However when they made the protocol they included a tag for Alarms (in the EU) / Emergency (in North America).

Reading up on the receivers with the RDS protocol / system built in they are designed to switch to the frequency broadcasting the Alarm / Emergency tag. Even if the radio is playing a “cassette” (which tells you how old this protocol is), a CD, connected via Bluetooth. Basically, if an RDS equipped radio is turned on it will tune to the station for the frequency the ambulance is broadcasting to.

The neat parts of this, the goal is to make it 10 to 15 seconds of alert, based on the speed of the ambulance. Which tells me the broadcast switch is tied to the Light and Siren switch, as well as either the ambulances GPS or ODB-II port, and the broadcast power is associated off that.

The people that came up with the idea said because Ambulances are getting stuck in traffic and or people are having accidents trying to get out of the way.

This is probably one of the items that really should be considered in Autonomous cars.

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