Thanks for the history Rich. I like it when we challenge requirements because there should be a rationale behind them. I wonder what bad experience caused the change in the ON/OFF symbols from 1/0 to |/O.
Also, when you get down to the nitty-gritty, the so called ON/OFF symbols are there so third party safety certifiers have a reference to use to make sure what is the designated ON or OFF of a product mains power switch. However, I prefer to use a detachable power cord as the mains disconnect device, when applicable. Finally, what is sometimes ridiculous about labels and symbols is where they are on a product and whether they can be seen under normal use. If the O/| symbols are next to a mains power switch located on the back of an instrument, what good is that? You can't see the symbols in normal use. However, when Company Industrial Design folks have their way, you most likely will be required to have a switch on the front of the product. Whether that is a mains disconnect or stand-by switch is left for discussion. Best regards, Ron Wellman From: [email protected] [mailto:[email protected]] On Behalf Of Richard Nute Sent: Friday, February 26, 2010 5:41 PM To: Kunde, Brian Cc: emc-pstc Subject: O and | symbols -- a bit of history The 0 and 1 harken back to rotary switches and CEE standards. Here is a quote from IEC 380, "Electrical Safety of Office Machines," 1972: If figures are used for indicating the different positions, the "off" position shall be indicated by the figure 0 and the position for a greater output, input, speed, cooling effect, etc., shall be indicated by a higher figure. The figure 0 shall not be used for any other indication, except that this shall not preclude the use of the figure 0 for the identification of an alphabetic or numeric key on an office machine. Ever see such equipment -- a rotary off-on switch with other positions such as receiving band??? Atwater Kent radios had them! Since that time, the 0 and 1 have morphed into the circle and line and variations thereof. Notice that, back in 1972, you could use the words "off" and "on." Now consider Brian's questions about the use of the 0 and 1. What have we done to ourselves??? Best regards, Rich - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
