Abstract: A silicon micro-transmitter chip is housed within top and bottom closures snap-fitted together by legs and catches on the two closures. The chip is mounted between two acoustic cavities in the closures by a plate part of a configured metal sheet having other strip parts extending through grooves in the bottom closure to its outside where the strips are bent to provide arms for surface mounting the entire device on a printed wiring board. The sheet serves both as a continuous strap for effecting such surface mounting and as an electrode for connecting a terminal of the chip to ground. Other terminals of the chip are connectable to the board by flat leads passing through other grooves in the bottom closure to its outside where they are bent for surface mounting purposes. The housing formed by the two closures includes an adhesive impregnated gasket for providing an acoustic seal between the two cavities as to which the air pressures therein are equalized by a vent hole in the plate.

Abstract: ABS thermoplastic material is rendered electrically conducting by the inclusion of carbon particles. When manufactured by a process of dry mixing of ingredients, melting, and molding, the material has desirably low sheet resistance even at relatively low levels of carbon content (as is desirable in the interest of plastic formability). The new material may be used in the manufacture of electret microphones.