Abstract: A base station microphone with a transmit bar and a monitor button, the latter being operable to actuate a switch to check for a clear channel before transmitting. The present invention relates to a simple mechanical interlock between the monitor button and the transmit bar, wherein the monitor button must be depressed before the transmit bar may be actuated for transmission. The improved interlock comprises a bell crank lever that has a portion disposed to block depression of the transmit bar. When the monitor button is depressed, the bell crank lever is shifted to move said portion from its blocking position.

Abstract: An improved microphone structure having a ball screen enclosing the transducer. The microphone body or handle has an annular shoulder at its upper end to provide an upstanding externally threaded projection. The lower part of the ball screen has an opening to receive the upstanding handle projection, the peripheral portion of the screen at the opening being turned inwardly and adapted to be secured to an internally threaded base ring. The base ring is threaded on the handle projection to secure the ball screen in place.

Abstract: A needle assembly for a phonograph pickup cartridge wherein the pickup needle coupler and shank are movable relative to a drive member which is disposed between the needle shank and the mechanoelectric transducer means, to vary the position of the needle tip with respect to the cartridge drive member along the lonitudinal axis of the cartridge, and thus cause predetermined selectable changes in the needle lever ratio which in turn causes changes in compliance and output of the cartridge-needle assembly.