| TYPE | USE | OPERATING PRINCIPLE |
|---|
| 1. CARBON | TELEPHONE MOUTHPIECE | VARIES CURRENT FLOW ACCORDING TO AUDIO RECEIVED |
| 2. DYNAMIC | GENERAL WIDE USE | GENERATES ELECTRICAL SIGNALS ACCORDING TO AUDIO RECEIVED |
| 3. ELECTRET | GENERAL WIDE USE | GENERATES ELECTRICAL SIGNALS ACCORDING TO AUDIO RECEIVED |
| 4. CRYSTAL, SPIKE AND CONTACT | SENSES WINDOW AND WALL VIBRATIONS | CONVERTS VIBRATIONS INTO ELECTRICAL SIGNALS |
| 5. PNEUMATIC
CAVITY | SENSES WINDOW AND WALL VIBRATIONS | CONVERTS VIBRATIONS INTO ELECTRICAL SIGNALS |
| 6. SHOTGUN AND
PARABOLIC | DIRECTIONAL SENSING OF SOUND, SPORTS, ENTERTAINMENT | FOCUSES SOUND VIBRATIONS COMING FROM ONE DIRECTION |
| 7. CAPACITOR OR CONDENSER | GENERAL WIDE USE | CONVERTS AUDIO INTO CORRESPONDING VARIATIONS CIRCUIT FREQUENCE |