In the 1980s, Casio's budget electronic instruments and its line of affordable home electronic musical keyboard instruments became popular. The company also became well known for the wide variety and innovation of its wristwatches. It was one of the earliest manufacturers of quartz watches, both digital and analog. It also began selling calculator watches during this time. Casio also introduced one of the first watches that could display the time in many different time zones of the world and with features like recording temperature, atmospheric-pressure and altitude. In the later years, Casio's wristwatches were fitted with receivers to synchronise with radio towers around the world and Global Positioning System for timekeeping accuracy.