VOX for P.A. systems

VOX for PA systems An annoying problem with PA systems is their tendency to whistle or "howl" due to feed back phenomena. There are a number of methods of avoiding the problem, the most obvious being the repositioning of the speakers in relation to the microphone. However, this is not always possible and the object of this article is to provide an answer for those difficult situations where feedback appears be "built in". It is well known that lowering the frequency be tween the microphone and the PA amplifier by about 5 Hz will reduce feedback in many situations when all else seems to fail, but a "frequency shifter" is an expensive piece of equipment and even then, its effectiveness is not always on a par with its cost. Since feedback requires time to build up, a simple solution to the problem would be to keep ossible the microphone switched off for as long as p, in fact, right up to the point at which speech begins. In other words, a voice operated switch or VOX. This design is ...