TONE BURST GENERATOR

摘要

A tone burst generator where a continuous tone voltage is applied across two series-connected semiconductor switches each having an ON state and an OFF state. A first control circuit controls the state of the first switch and the variable impedance in an intermediate region between its ON and OFF states to cause gradual, well-defined OFF/ON and ON/OFF transitions of the first switch. As a result of these first switch transitions, a voltage tone burst is generated that has precisely defined edges to eliminate clicking noise. The continuous tone voltage is of only one polarity--it has a non-zero DC component and an AC component having a peak-to-peak variation less the twice the magnitude of the non-zero DC component. A second control circuit controls the state of the second switch and the variable impedance in an intermediate region between its ON and OFF states to cause well defined ON/OFF and OFF/ON transitions of the second switch. The second switch OFF/ON transition reduces the voltage tone burst to have a substantially zero AC component.