What do you mean by "stand by mode?"
Basically when you first power it up, and prior to choosing a platform (PC, xbox 360, ps3), the display will show "---". The manual, page 19, refers to this as "standby" mode. It's also referenced again when instructing the user regarding turning the fan on/off.
I'm just wondering if there's a way to put it on standby and switch platforms without powering it down, then back up again.
Turning off the XBOX disconnects the wheel and puts it into standby mode. However, doing the same on the PS3 the wheel will stay in PS3 mode. I can't speak for PC; but I assume the same as PS3.
Doesn't look like there is a way to go into standby without turning it off when connected to PS3.