Keywords: 555 Mk-sp Diagram.svg Circuit diagram of a 555 Astable circuit with variable mark-space ratio The design equations can be found http //en wikibooks org/w/index php title Practical_Electronics/Astables/555 Design_equations_2 here Own drawing made in Inkscape 0 43 2006-06-20 jjbeard PD 555 timer IC Astable circuits |