What are the other symbols, and how do I tell the lookalikes apart?
This lesson is about two pairs of lookalikes: the two grounds, and the family of resistors with extra marks.
The two grounds
- Chassis ground: a horizontal line with slanted lines (like a rake) hanging from it. It marks the metal case or chassis of the equipment.
- Earth ground: three parallel horizontal lines getting shorter. It marks a connection to the actual earth.
Resistors with extra marks
A plain resistor is a zig-zag or box. Extra marks change the meaning:
| Mark on the resistor | Meaning |
|---|---|
| Diagonal arrow through it | Variable resistor |
| Third lead or arrow touching the middle | Adjustable (arrow) or tapped (plain lead) resistor |
| "t" (with a small circle) | Thermistor (its resistance changes with temperature) |
| Arrows pointing in (light) | Photoresistor (its resistance changes with light) |
You now know
- Chassis ground is a horizontal line with slanted lines; earth ground is three parallel lines getting shorter.
- A diagonal arrow through a resistor makes it variable.
- A third lead or arrow touching the middle is an adjustable (arrow) or tapped (plain lead) resistor.
- A "t" marks a thermistor, and arrows pointing in mark a photoresistor.