<P> Detailed rules for reference designations are provided in the International standard IEC 61346 . </P> <P> It is a usual although not universal convention that schematic drawings are organized on the page from left to right and top to bottom in the same sequence as the flow of the main signal or power path . For example, a schematic for a radio receiver might start with the antenna input at the left of the page and end with the loudspeaker at the right . Positive power supply connections for each stage would be shown towards the top of the page, with grounds, negative supplies, or other return paths towards the bottom . Schematic drawings intended for maintenance may have the principal signal paths highlighted to assist in understanding the signal flow through the circuit . More complex devices have multi-page schematics and must rely on cross-reference symbols to show the flow of signals between the different sheets of the drawing . </P> <P> Detailed rules for the preparation of circuit diagrams, and other document types used in electrotechnology, are provided in the international standard IEC 61082 - 1 . </P> <P> Relay logic line diagrams, also called ladder logic diagrams, use another common standardized convention for organizing schematic drawings, with a vertical power supply rail on the left and another on the right, and components strung between them like the rungs of a ladder . </P>

What is a cell in a circuit diagram