Номер патента: FR2783601A1. Автор: Christian Claeys. Владелец: CLAEYS ETS. Дата публикации: 24-03-2000.
A beer barrel (1) supplies a bar pump through an electrovalve (5) and a transparent pipe (2). A periodically energized source of infrared radiation (3) is located on one side of the pipe and a photosensitive sensor (4) on the other such that a change from beer to mousse is detected by an electronic circuit and used to switch off the beer supply by operating the electrovalve (5).