Green Wave?

[benb]

Curious to know whether anyone can answer me a very long-running query.

Back in the late 1980s trips between home and Halifax from Gig Mill, Ripponden would be on something like this:
flic.kr/p/5FwR6G

As we approached Halifax a box in the cab would beep. Bip-space-bip-space-bip-space-ba-bo-ba. Hope you follow that!

After a while I sort of realised that the final sequence would usually follow the traffic lights going green.

I read another report from West Yorks County Council about Fire Appliances having a 'green wave' device that would change traffic lights in their favour.

Does anyone know what this device was and what it's purpose was?

Thanks

Ben

[ratty]

Haven't a clue what you are describing, and I was very much driving these in the late 80's!!!Andy 1 you any ideas??

[stantheman]

It just sounds like the drivers radio back to base.