Abstract: A bi-directionally insertable elastomeric ear plug for sealing an ear canal has an outer body defining two identical expansible and collapsible fluid chambers. A fluid, preferably air, is sealed within the outer body, and a passageway is defined between the two fluid chambers for selectively placing the chambers in fluid communication with each other. An elastically displaceable wall bounding the passageway acts as a two-way pressure responsive valve operative to close the passageway and thereby maintain an equilibrium condition with one of the chambers expanded and the other collapsed, and to temporarily open the passageway when one of the chambers is squeezed. The collapsed chamber is insertable into an ear canal with the aid of an elongated semi-rigid core member extending within the outer body. Thereafter, the expanded chamber can be squeezed to expand the collapsed chamber inside of the ear canal to obtain a comfortable yet tight form-fitting seal.

Abstract: A push-button switch comprises a housing having a substantially cylindrical interior portion. It also includes a movable switching member, disposed substantially within the interior of the housing and having a reciprocally movable plunger with successive released, latched and depressed positions relative to the housing interior portion. Functional surfaces of substantially cylindrical form are disposed adjacent and in a substantially fixed position relative to the interior portion of the housing and include guiding surfaces aligned in the direction of movement of the plunger. The plunger has members, interengaging with the guiding surfaces, for preventing rotation of the plunger during reciprocal movement of the plunger. The movable switching member also includes a rotatable latch ring, preferably C-shaped, disposed on the plunger and having a radially extending lug. The plunger also has members for holding the rotatable ring in a fixed latitudinal position about a portion of the plunger.