| Prefix | Description |
|---|---|
| A | Separable Assembly |
| AR | Amplifier |
| AT | Attenuator; Isolator |
| B | Blower, Motor |
| BT | Battery, Battery Cell , Solar Cell |
| C | Cap: Fixed, Variable, Multi-element |
| CB | Circuit Breaker, Network protector |
| CP | Connector Adapter, Coupling |
| D or VR | Breakdown Diode, Zener Diode |
| D | Diode, Transzorb |
| DC | Directional Coupler |
| DL | Delay Line |
| DS | Display, Lamp, LED, Visual Indicator |
| E | ANT, Terminal, Ferrite Bead Ring, Misc. Electrical Part |
| F | Fuse |
| FD* | Fiducial |
| FL | Filter |
| G | Generator, Oscillator |
| H | Hardware |
| HY | Circulator |
| J | Connector, Jack, Most fixed of pair |
| K | Contactor, Relay |
| L | Coil, Inductor |
| LS | Loudspeaker, Buzzer |
| M | Meter |
| MG | Motor-generator |
| MH* | Mounting Hole |
| MK | Microphone |
| MP | Mechanical Part |
| P | Conn., Plug, Most movable of pair |
| PS | Power Supply |
| Q | Transistor, SCR |
| R | Res: Fixed, Variable, Multi-element |
| RT | Thermistor, Thermal Resistor |
| RV | Symmetrical Varistor |
| S | Switch |
| T | Transformer |
| TB | Terminal Board, Terminal Strip |
| TC | Thermocouple |
| TP** | Test Point, In-circuit Test Points |
| U | Inseparable Assembly, IC Pkg. |
| VR | Voltage Regulator |
| W | Wire, Cable, Cable Assembly |
| X | Holder: Fuse, Lamp, Battery Socket |
| Y | Crystal, Crystal Oscillator |
| Z | Balun, General Network, Phase Shifter |
* These class letters would not appear in a parts list as they are part of a PCB and not an active electronic component.
** Not a class letter, but commonly used to designate test points for maintenance purposes.
Note: The above list is not exhaustive. See the standard list of class designation letters in ANSI Y32.2/IEEE Std. 315, Section 22 and the Index.