How can I switch fuel requests at my LTN depots through my circuit network?

[Bushdoctor]

Hello,

Some of my LTN-stations function as fuel-requesters for my depots. I would like to be able to switch the requested fuel type at those stations through my circuit network, at a distance, and all at the same time. (So I don't have to visit each depot and manually switch the requested fuel type)

I've got a feeling that the solution to my question would be somewhere along the lines of 'Instead of a certain fuel type, request the letter A at your fueling stations, and at your Headquarters designate the desired fuel type to that letter A through a combinator.', but the problem is that I have no idea how to do that. If someone could tell me what combinators to use, how to connect them, and what settings to make, that would be very much appreciated.

Thank you.

[Serenity]

To change a signal use an arithmetic combinator and multiply by 1 or add 0