Signal flow on a schematic is conventionally shown in which direction?

In AV system schematics, signal flow is traditionally depicted from left to right. Inputs (sources) are placed on the left, and outputs (displays, speakers) are on the right. This makes signal tracing intuitive and consistent for documentation and troubleshooting.

“Standard AV system drawings depict signal flow from left to right, starting at source and ending at output, to provide logical signal tracing.”

— CTS Exam Guide, Documentation and Schematics Chapter