There is a convention of the reference designator used for each kind of component. Here are some of them (substitute a cardinal value for <n>):
| Prefix | Component type |
|---|---|
| R<n> | Resistor |
| RN<n> | Resistor Network |
| FB<n> | Ferrite Bead |
| L<n> | Inductor |
| C<n> | Capacitor |
| B<n> | Battery |
| F<n> | Fuse |
| J<n> | Connector |
| P<n> | Connector (usually plugs that mate with J<n>) |
| K<n> | Relay |
| S<n> | Switch |
| T<n> | Transformer |
| TP<n> | Testpoint |
| M<n> | Motor |
| D<n> | Diode |
| Q<n> | Transistor |
| U<n> | IC |
| X<n> | Crystal |