| 摘要 |
PURPOSE:To make it possible to adjust a muting level by a simple circuit, by level- shifting an output of the signal meter driving circuit, applying it to the emitter of a transistor, and obtaining a muting control signal. CONSTITUTION:The emitter output of the emitter follower transistor (TR)Q7 for driving the signal meter M is level-shifted through the diode Q9, and it is applied to the emitter of the TRQ8. The stabilized voltage V1 is divided by the resistance R8 and the variable resistance R9, it is applied to the base of the TRQ8, and the collector of the TRQ8 is connected to the AC ground terminal capacitor C3 of the tank circuits L, C2. When the meter driving output is less than the prescribed level, the TRQ8 is turned on, the potential of C3 is prescribed as a direct current, the bias point of the switching TR's Q3-Q6 is varied, the switching operation is stopped, and the muting control is executed. The base potential of the TRQ8 is varied by making the resistance R9 variable, and the muting level is adjusted. |
