SOME MORE SYMBOLS

Meters are indicated as circles. Sometimes the circle has an arrow inside it, and the meter type, such as mA (milliammeter) or V (voltmeter), is written alongside the circle, as shown in Fig. 1a. Sometimes the meter type is indicated inside the circle, and there is no arrow (see Fig. 1b). It doesn’t

Fig. 1. Meter symbols: (a) designator outside; (b) designator inside.

matter which way it’s done as long as you are consistent everywhere in a given diagram.
Some other common symbols include the lamp, the capacitor, the air-core coil, the iron-core coil, the chassis ground, the earth ground, the alternatingcurrent (AC) source, the set of terminals, and the black box (which can stand for almost anything), a rectangle with the designator written inside. These are shown in Fig. 2.

Fig. 2. More common schematic symbols: (a) incandescent lamp; (b) fixed-value capacitor; (c) air-core coil; (d) iron-core coil; (e) chassis ground; (f) earth ground; (g) ac source; (h) terminals; and (i) and black box.