| 摘要 |
<p>The audio prothesis has an electrical supply (1), a microphone (2), a group of amplifying, regulating, filtering and analogue circuits (3) and an earphone (4). The microphone delivers an input signal and the earphone receives the output signal. A sound level regulating potentiometer (5) is situated between a pre-amplifier (6) and a push-pull type output circuit (7) connected to the terminals (8,9) of the earphone by two lines (10,11). The earphone also has a supply terminal (12). Between the supply terminal and the pre-amplifier output there is an intermediate system which takes account of sudden variations in emitted sound in order to reduce the occurrence of noises and eliminate them. This is achieved by comparing the variation of the real value of the input signal during a given time with a pre-established ceiling value of the variation. When the input signal variation is equal to or greater than the ceiling value the output signal is stopped. This intermediate system may consist of a rat-race circuit (13).</p> |
