------------Original Message: Date: Wed, 12 Sep 2007 19:56:02 -0400 From: "Roy J. Tellason" <rtellason at verizon.net> Subject: Re: 8-bitters and multi-whatever On Wednesday 12 September 2007 19:45, Ensor wrote: Yup! But my point is that in prototyping some small SBC the rs232 stuff is about the only thing on there typically that needs other than logic power (+5V) unless there's some analog stuff there on the board that needs it. MIDI, in every implementation I've ever seen, uses only a 5V supply. I never did understand why current loops weren't used more... ======================== -----------Reply: On short runs you can usually get away with TTL levels on RS-232 as long as you limit the input voltage swing with a resistor and a couple of diodes or use an optocoupler.