I'm working on a simple serial control project and need some ideas please.
My application requires that a master unit transmit and recieve from as
many as 30 slave units.
The messages are only a byte long and the master will pole all slaves. I
need a way of powering and communicating with the slaves via a 3 pin mic
lead.(sheilded twisted pair). I would also like to use the system on
exsisting audio lines thus leaving only one wire for comms.(and a ground).
The final problem is the comms need to be inaudible(out of the audio
range.) Natsemi have a powerline modem chip whick will operate on a carrier
up to 50 Khz however it needs the mains zero crossing for synchronising and
im running dc. Any Ideas Huh?!!

Cheers
Richard Bond..
richardb@mailbox.uq.edu.au