What is the rs-485 protocol for controlling old flipdot displays?
So, I realize I'm a bit late to the party here, but maybe someone will still find this useful. I've documented the protocol used by Luminator MAX 3000 and Horizon signs at https://alusch.github.io/flipdot-protocol. I think your sign is a bit older and uses a slightly different protocol, but hopefully it's at least a decent starting point.