I'm planning on setting up a sensor network around my house using a Cat5 Cable as both the power source and the signal line for the sensors, I'm planning on using RS-485 Transceivers and and Arduino's for the sensors.
From reading through many application notes and whatnot from TI and Maxim they all talk about having a failsafe so an Idle Bus goes to a known state.
If I use a master/slave setup why is this needed? If the master assumes that no slave will transmit unless requested to, and the slaves are constantly listening for their own address. It seems like this could be expanded for quite a bit of redundancy, without worrying about the state of the line when it's turned on.
Is there something I'm missing?