The motherboard is the central printed circuit board in devices like computers. It connects the main computer components to one another. A monitor displays images from devices like computers without creating a permanent record. Modern monitors use LCD screens while older ones used CRT screens. A headset combines a headphone and microphone for hands-free calling or communication at a computer. It allows comfortable conversation and typing. An automatic voltage regulator automatically maintains a constant voltage level using electromechanical or electronic components. It regulates AC or DC voltages. Speakers are devices that convert electrical signals into audible sound. External speakers have internal amplifiers and connect via audio jacks or cables, while some use USB for power.