What is component 4 in figure T-1?

Component 4 in Figure T-1 represents a multi-cell battery. This schematic symbol is composed of alternating long and short parallel lines. The long line denotes the positive terminal of the battery, while the shorter, thicker line denotes the negative terminal. By stringing multiple long and short pairs together, the schematic indicates a battery made of several individual cells connected in series. It is important not to confuse this with a ground symbol, which has decreasing line lengths forming a triangle shape, or a capacitor, which features lines of equal length.