Favre-Leuba launched the Bivouac in 1962. It was the first mechanical wristwatch with an aneroid barometer for altimetry and air pressure measurement. It is lightweight and, at 40 mm in diameter, no larger than a conventional chronograph. Thanks to its reliability and precision, ease of operation and excellent readability, it quickly became part of the essential equipment of mountaineers, pilots, researchers and anyone else who conquers seemingly insurmountable frontiers.
Using the rotating bezel – which includes a scale of 3,000 m above sea level, whereby each division of the scale corresponds to 50 m – and the red hand, the altitude above sea level can be set at the beginning and read continuously. Along with the outer dial ring, the red hand shows additionally the air pressure in millibars. If the rotating bezel is set to zero, the altitude (bezel) and the average prevailing air pressure (dial ring) are directly opposite. If the red hand now goes to a lower value, then air pressure is decreasing, meaning that the weather conditions are deteriorating; if it points higher, the weather will be beautiful.