A monitor is an output device that displays information in pictorial form. A monitor usually comprises the visual display, circuitry, casing, and power supply. The display device in modern monitors is usually a skinny film transistor liquid display (TFT-LCD) with LED backlighting having replaced cold-cathode lamp (CCFL) backlighting. Older monitors used a beam tube (CRT). Monitors are connected to the pc via VGA, Digital Visual Interface (DVI), HDMI, DisplayPort, Thunderbolt, low-voltage differential signaling (LVDS) or other proprietary connectors and signals.