where does the power on symbol come from
Power symbol The well-known on/off power symbol was the result of the logical evolution in user interface design. Originally, most early power controls consisted of switches that were toggled between two states demarcated by the words On and Off. As technology became more ubiquitous, these English words were replaced with the universal symbols line "|" and circle "o" (typically without serifs) to bypass language barriers. This standard is still used on toggle power switches.
Yield sign The sign went through several changes from its original design to the sign used today. Originally invented in 1952 and was added to the MUTCD in 1954, the sign used the "keystone" shape, before adopting the more readily recognized triangular shape. In 1971, the sign evolved into its modern version and changed from yellow to red.