This is not a circuit diagram. The symbols used are an international ... A circuit has to have a power source and that is often a cell. The short line of the symbol is the negative terminal.

These could be batteries, solar panels, or a power supply connected to ... This circuit diagram shows the same circuit, but uses circuit symbols to represent the cell, bulb and wires.

The technical report, ISA-TR5.1.01-ISA-TR77.40.01-2012, Functional Diagram Usage, expands upon and illustrates usage of function block symbols and functions, and prepares examples in development of ...