For input transducer : 

• LDR converts brightness (of light) to resistance.
• Thermistor converts temperature to resistance.
• Microphone converts sound to voltage.
• Variable resistor converts position (angle) to resistance.

For output transducer : 

• Lamp converts electricity to light.
• LED converts electricity to light.
• Loudspeaker converts electricity to sound.
• Motor converts electricity to motion.
• Heater converts electricity to heat.