A signalling device (10) adapted to make a percussive sound, for example,
under water. The signalling device (10) may be attached to a pressurized
fluid source, such as a diver's compressed air supply, the device (10)
including: a housing (12) having a passageway (22), at least in part, for
communication with the fluid source; a valve member (34) located in the
passageway (22) and movable between a closed position in which it
substantially blocks the passageway (22), and an open position in which
fluid may flow through the passageway (22); biasing means (42), such as a
spring, biasing the valve member (34) towards the closed position, wherein
the valve member (34) reciprocates between the open and closed positions
when a pressure difference above a set value exists on either of the valve
member (34) to produce a perscussive sound.
