Abstract: A two-tone signal generator, serving as a horn for automotive vehicles, crises two complementary half-shells whose interior is divided by a common partition into two convoluted wind channels of different length resonating at different frequencies and opening into a common outlet. The inlet to the wind channels comprises a central duct with two lateral branches terminating at a pair of nipples to which a hose from an air blower can be selectively fitted; the junction of the branches with the central duct is an enlarged space containing a freely movable rubber ball which automatically blocks one nipple when air is admitted through the other nipple. The duct communicates with the two wind channels via respective lateral chambers formed in the two half-shells, each chamber being partly closed toward the outside by a lid provided with an eccentric air slot.

Abstract: An electromagnetic acoustic alarm device including a casing formed in part by a bell-shaped wall which defines together with a membrane secured to the casing by means of the bell-shaped wall a chamber, the front portion of the wall provided with at least one opening and a rotatable external plate of the same configuration as the wall front portion having at least one opening for registration to a selected extent with the wall opening so as to adjustably attenuate the high frequency sound component of the device.

Abstract: A helix of wire having predetermined dimensions is encircled by a sleeve of selected material which conforms to the exterior surface configuration of the helix. When a gas is applied into one end of the helix-sleeve combination, an audio frequency signal appears at the other end of the helix-sleeve combination having a frequency which increases in steps proportional to the entrance pressure of the gas flowing through the helix-sleeve combination, or proportional the changes in the mass rate of flow of the gas through the helix-sleeve combination.

Abstract: A combination smoke and heat detector alarm including a self contained stored energy source in the form of a cylinder of compressed gas. A T-fitting connects to the cylinder and feeds separate conduit systems leading to individual sounding devices. A fusible element is interposed in one of the conduit systems to automatically permit transfer of the compressed gas to a first sounding device upon the presence of elevated temperatures. A solenoid operated switch is interposed in the other conduit system to normally prevent the flow of gas. The solenoid is responsive to a smoke detector and is wired to open the solenoid valve upon sensing the presence of a predetermined concentration of smoke.