The requirement of large numbers of lactobacillus counts, which are done by spreading aliquots of saliva-glucose broth mixtures with sterile bent glass rods over the surfaces of tomato juice peptone agar (pH 5.0) plates, led to the development of a simple, inexpensive motorized device to facilitate this process. Comprised of a conventional three speed phonograph motor and turntable, the instrum...

Audio signal preamplifiers (preamps) represent the low-level end of the dynamic range of practical audio circuits using modern IC devices. In general, amplifying stages with input signal levels of 10mV or less fall into the preamp category. This section discusses some basic types of audio preamps, which are: ■ Microphone— including preamps for dynamic, electret and phantom powered microphones, ...

What role do audiences play in the formation of media? influence consumer practices have on This article explores relationship between media and from a historical sociological perspectives. Using literature review communications history, this paper analyses outlines key terms concepts for understanding different perspective. As studies is an important part social sciences, conceptualising as pr...

Between 1877 and 1896 Edison and Berliner developed their cylindrical and disc phonograph systems, providing us with the new ability to store audio signals and to retrieve them from storage by electro-mechanical means. About half a century later, and nearly 30 years after Lee DeForest had initiated electronics with the first vacuum tube (the triode audion), the phonograph disc was joined by mag...

The introduction more than thirty years ago of the term 'impedance' by Mr. Oliver Heaviside has been productive of very great convenience in the theory of alternating currents of electricity. Unfortunately, engineers have not seemed to notice that the idea may be made as useful in mechanics and acoustics as in electricity. In fact, in such apparatus as the telephone one may combine the notions ...