Abstract: An acoustic device is described that comprises an acoustic channel extending through its housing and an acoustic valve disposed in the acoustic channel. The acoustic valve is configured to determine a passage of sound through the housing via the acoustic channel. The acoustic valve comprises a deformable shape forming a deformable perimeter of the acoustic channel, and an actuating mechanism configured to exert an actuating force deforming the deformable shape causing the deformable perimeter to move and change the passage of sound.

Abstract: A cartridge for a video disc stylus having a stylus-position sensor, including an electrode mounted to the cartridge walls. An appendage is provided on the cartridge wall to position the sensor electrode proximate the stylus, the appendage being contoured to accept a preformed sensor electrode. The sensor electrode is formed from sufficiently resilient material to recover from deformation during electrode-appendage engagement and constrain itself to a particular position in the cartridge by compressive forces developed between the electrode and the appendage.