PSK31 is a digital mode used in amateur radio that allows operators to communicate using keyboard-to-keyboard text. It was developed in the late 1990s and is known for its efficiency in low-bandwidth situations, making it ideal for weak signal conditions. The mode uses phase shift keying to transmit data, which helps to minimize interference and improve clarity. This mode operates at a speed of 31.25 baud, allowing for quick exchanges of information. PSK31 is popular among amateur radio enthusiasts because it requires minimal equipment and can be used on various frequencies, making it accessible for operators worldwide.