To convert the electrical signal from an addressable control panel into light for transmission between buildings, and then back to electrical energy for use, you would use a __________.

• A. Transducer
• B. Amplifier
• C. Transformer
• D. Converter

Answer: (A)

The key idea here is energy-form conversion. You’re taking an electrical signal and turning it into light to send between buildings, then converting that light back into electrical energy for use. A transducer does exactly that—it's a device that converts energy from one form to another. In this system, the electrical energy drives a light source to emit photons (electrical to optical), and the incoming light is converted back to an electrical signal by a photodetector (optical to electrical). The other options don’t fit: a transformer changes voltage or current within electrical form, an amplifier increases signal strength but doesn’t change the energy form, and a converter is a more general term that doesn’t specify the electrical-to-light and light-to-electrical energy conversion.