Analog panel meters are instruments that measure variables such as pressure, flow, temperature, speed, current, and voltage. They display values on a dial, usually with a moving pointer or needle. Many types of analog panel meters are available. The most common type accepts a single input from a temperature sensor such as a thermocouple or resistive temperature device (RTD). Analog panel meters can also accept pulses, frequencies and signals. Multiple channel devices are available. With the advent of digital technology, analog panel meters are used less frequently; however, some applications still require them. For example, analog panel meters are well suited for applications that require users to scan many devices to determine whether an individual meter is incorrect. For improved usability, analog panel meters with anti-glare, mirrored, and illuminated faces are available.