| 摘要 |
PURPOSE:To reduce the power consumption for the receiver using the cell as the power source by actuating the light emitting diode in the detuning state not in the tuning state. CONSTITUTION:The reception wave is detectes at diode 4 via antenna 1, high frequency circuit 2 and intermediate frequency circuit 3 each, and the detection output is supplied to low frequency circuit 6 via variable resistance 5. The output of circuit 6 is sent to earphone jack 7. Resistance 31 feeds the output of diode 4 back to circuit 3 to function to form part of the AGC circuit which controls the gain of circuit 3. When the reception signal is intensified through tuning, the output of diode 4 features the negative potential. Thus the AGC operates to lower the gain of circuit 3. In this instant, Tr 8 is turned off with no emission of light emitting diode 9 because the base of Tr 8 features the negative load. At the detuning time, the AGC does not operate contrarily with the base of Tr 8 featuting the positive potential, and as a result Tr 8 is turned of with emission secured for diode 9. At the same time, contact 71 of jack 7 lights up diode 9 to alarm for detachment of the plug. |
