Hey is there anyone out there with experience talking via RS-232 / RS-485 adaptors to Aprilaire HVAC control systems?

I was wondering if you can confirm that you can communicate to these systems using a terminal emulator (like Putty) via Serial? I get garbage characters when I try to connect, looks like the system is reporting/working but it's illegible - I've tried all the character sets available without any luck for example if I just do a SN? command I get this:

Yc▒▒▒▒

I am using a DTECH USB->RS-485 adapter not the AprilAire box in full disclosure. No idea what is happening - any clues from those who have done this before?

Is this a character set issue?

Thanks

--Artful