What is component 4 in figure T-3?

In figure T-3, component 4 is drawn as a vertical line with three shorter lines branching outward and upward from the top, resembling a Y-shape or a pitchfork. This is the universal schematic symbol for an antenna. The antenna symbol represents the point in the circuit where radio frequency energy is radiated into space or received from it. It is distinct from a ground symbol, which uses decreasing horizontal lines at the bottom of a circuit, or a dummy load, which is typically drawn using a standard resistor symbol.