The HPW 11 signalling hooter is a signalling device for warning and calling which, thanks to its sturdy housing, can be used indoors in both dry and damp rooms as well as outside. The version with telephone call relay allows the device to be used as an additional, loud acoustic signalling device for a telephone. The driver system consists of a strong, non-polarised lectromagnet, whose striker hits the diaphragm between 100 and 120 times a second. The housing of the signalling hooter is made of impactresistant thermoplastic. A self-sealing grommet M20 is proveded as cable gland for cable diameters of 8 to 1 mm. The signalling hooter with telephone relay is equipped with two self-sealing grommets M20.