I think there's two issues here... 1) There is a standard for the symbols for the three types of ground... earth (line with bars), Chassis (pitchfork), and circuit (upside down triangle - or arrow pointing down). These should be used appropriately but many do not use these correctly at all - and in many situations it doesn't really matter. For most pic circuits, whether or not it is earth, chassis and/or circuit ground is irrelevant, as long as everything which needs to be tied electrically together is tied electrically together. Because of this many use these symbols interchangeably, even though they are not technically the same. So when reading a circuit, you need to think about which ground is *really* meant, and not blindly assume the symbols are used correctly. 2) The shown circuit is drawn in a very dangerous way. It uses the earth ground symbol instead of circuit ground. It's dangerous because it does so in a circuit where interconnecting circuit ground and earth ground would result in a dangerous situation, since the most common source of 115VAC (at least in the states) has one leg attached to earth ground. What shocks me is that this schematic appears to be from the official onsemi datasheet. It makes me trust onsemi less, since this is potentially a very bad error. Makes you wonder what other but less obvious dangerous errors exist in other (sort of the Brown M&M effect). -forrest Vasile Surducan wrote: > On 7/12/08, Geo wrote: > >> On 12 Jul 2008, at 3:03, Vasile Surducan wrote: >> >> >>> That's not "earth" nor 'neutral". Is just a symbol representing the >>> ground of the circuit (where ground = reference for measured >>> voltages). >>> >>> >> No it is The Earth. >> see for example:- >> http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/earth/earth.htm >> or - if line wraps use:- >> http://tinyurl.com/5fhmmy >> > > Guys, read deep into the schematic and think twice everytime you are > reading it. The symbol must not be taken as you have been teached at > school without thinking. > Those three neurons (two from the brain and one from the pants) must > be put at work... > :) > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist