Scope capture of rs485 signal

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I dont know if this is the right place to ask since its not related to audio at all.

This is a capture of data on a rs485 between two public fire alarm systems in a building.

Having some random com-failiures i decided to scope the line.

I would need a diff probe but i had to do this single ended.

Would this be a good measurement/indication of the data bits being ok?

From what i can see there is around 0-5V on the line.

Maybe i get nothing usefull out of this, what do you think?

https://postimg.org/image/9i1axk3r5/
 
It looks like there is some lower frequency modulation of that data stream, possibly power line hum.

But on a balanced line such as is RS485, that should not be an issue (within reason). Can you scope after the RS485 receiver chip? Lets see what the raw TTL data looks like on the PC board.
 
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