1. Schematic Symbols The Key to Understanding Wiring Diagrams

2. Battery Supplies a Direct Current (DC) source

3. Resistor Resistors impede the flow of electricity

4. SPST Switch Opens (off) or closes (on) an electrical circuit

5. Light Bulb Converts electricity into light

6. Fuse Only allows a predetermined amount of current (AMPS) to pass through and if that amount is exceeded it will melt in half (open)

7. Capacitor Blocks Direct Current (DC) flow, but allows Alternating Current (AC) to pass through

8. Diode/Rectifier Allows current to flow through only one direction

9. Transistor A solid-state electronic device that is used to control the flow of electricity in electronic equipment and usually consists of a small block of a semiconductor (as germanium) with at least three electrodes

10. Motor Converts electrical energy into motion

11. Electric Fuel Pump FP A motor driven pump, which supplies fuel to the engine

12. Chassis Ground Connects the circuit to the metal body or frame of the vehicle using the body as a conductor in the circuit

13. Ground Connects the circuit to the metal body or frame of the vehicle using the body as a conductor in the circuit (More commonly used than chassis ground)

14. Relay An electromagnetically controlled switch

15. Electromagnet Becomes magnetic when Direct Current (DC) is passed through it

16. Light Emitting Diode A one-way check valve for electricity that lights up when current is passing through

17. Variable Resistor The resistance to the flow of electricity can be adjusted

18. Variable Capacitor A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C circuits (tuners) to set the resonance frequency, e.g. to tune a radio (therefore they are sometimes called tuning capacitors)capacitorL/C circuits

19. Transformer/Coil By appropriate selection of the numbers of turns (N), a transformer thus allows an alternating voltage to be stepped up — by making NS more than NP — or stepped down, by making it less. alternating voltage The secondary induced voltage VS is scaled from the primary VP by a factor ideally equal to the ratio of the number of turns of wire in their respective windings:

20. Rotary Switch Multi-position switch like the one used in the DVOM!

21. Horn/Speaker Converts electrical energy into sound