| 摘要 |
<p>A volume level indicator using l.e.d.s., in partic. for building into a loudspeaker cabinet, is designed to operate without an additional power source, deriving its energy from the previous stage, in partic. the power amplifier. The l.e.d.s. are controlled by transistors in a circuit connected in parallel with the loudspeaker via a resistor and rectifying diode. A parallel capacitor smooths are loudspeaker signal and the resistor protects the transistor circuit against fast discharge pulses. The transistor and associated resistors produce a stabilised reference voltage.</p> |
