Abstract: A device for housing a sound-emitting transducer including a housing and a cap. The housing has a chamber defined by a cylindrical sidewall and an endwall with apertures. The cap mounts to the housing, and has apertures that can register with the apertures in the endwall. A groove is formed between the cap and teeth formed at its circular outer periphery. The cap's circular lip is inserted into the groove by deforming the cap slightly. Thus, relative movement is permitted between the cap and housing for registering and de-registering the apertures on the cap and housing. This controls the volume of the sound-emitting transducer.

Abstract: A controller, either a microprocessor or finite state machine, is used to generate a pulse train whose frequency and duty cycle can be varied to alter the frequency and amplitude of the output of a driven audio transducer. The ability to control both frequency and amplitude allows programmatic synthesis of many audio effects such as steady tones, warbles, beeps, sirens and chimes with no hardware or circuit changes. The transducer can be a piezoelectric bender or a speaker. The output of the controller controls a switch that builds current in an inductor when the switch is on. When the switch is turned off, the energy stored in the inductor is dumped into the audio transducer, either directly or through intermediate capacitor storage. This allows the generation of voltages across the transducer many times the supply voltage.

Abstract: A fastener, such as a housing, for mounting to a structure, such as a panel, that has an aperture formed therethrough. The fastener includes a shank member and an annular nut member that is configured to align coaxially with the shank member. The shank member is inserted through aperture in the structure and the nut member is placed on the shank member. Teeth on the radially outwardly facing surface of the shank member engage a pawl, such as one or more teeth, on the radially inwardly facing surface of the nut member to lock the nut member to the shank member. Removal of the nut member is effected by rotating the nut member to disengage the pawl from the teeth, thereby permitting longitudinal displacement of the nut member off of the shank member.