Abstract: A laser level with a sensorless DC motor controller having a feedback sampling circuit connected in parallel with the coil to sense back EMF. An integrator provides a feedback signal from the sensed back EMF, which the amplified difference from a reference level is used as a pulse width control signal. A pulse width modulation generator uses the control signal to generate variable “on” time pulse widths for each motor drive pulse such that high resolution is provided to the DC motor, permitting accurate rotor position at low rotational speeds. It is emphasized that this abstract is provided to comply with the rules requiring an abstract to allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that is will not be used to interpret or limit the scope or meaning of the claims.

Abstract: An air introduction system (10) provides an active noise control system which includes a speaker assembly (28) in which the speaker support ring (36) is mounted to a speaker housing (32) without fasteners. In one speaker assembly, the speaker housing includes a plurality of extensions (40) which extend radially from an outer periphery of the speaker housing (32). The speaker support ring includes an edge (42) which at least partially surrounds the extensions (40). In another speaker assembly, the speaker support ring (50) includes a plurality of apertures (52) through a flange (54) which closely fits a speaker housing (32). The housing edge (54) and the speaker protection cone edge (56) are heated to a melting point of the material and the speaker support ring (50) is sandwiched therebetween. Heated material from the housing edge and the speaker protection cone edge pass through the apertures (52) to provide an effective bond therebetween.

Abstract: The transverse partition for separating an exhaust volume into two adjacent chambers includes at least one gas flow passage between the two chambers, the gas flow section through the passage being modifiable under drive from the difference between the pressures on the two sides of the partition. The partition comprises a wall pierced by at least one slit defined between two adjacent edges of the wall, which wall is elastically deformable under drive from the difference between the pressures on the two sides of the partition, between a rest position in which wall continuity is ensured, the two edges of the slit being substantially touching, and a deformed position in which the two edges of the slit are spaced apart so as to define said gas-flow passage between them.