| 摘要 |
PURPOSE:To eliminate the shock noise that is produced when a selection switch is changed over, by connecting both an FM wave detector and a calibrating oscillator to the common load resistance with the same working point when the level is set in the magnetic recording of the broadcast. CONSTITUTION:An FM wave detector 1 and an oscillator 2 are selected by a switch 3', and the bias current is supplied from a constant voltage source 7 to a transistor (TR)7 or 12 for constant current source. Thus the working is controlled for both the detector 1 and the oscillator 2. The detector 1 and the oscillator 2 are constituted at the same working point and by sharing a common load resistance 13. When the oscillator 2 is selected by the switch 3', the oscillation signal of the oscillator 2 emerges at the common load point P. Thus the circuit is opened when viewed at the side of the detector 1, and the oscillation signal is delivered to an output terminal 16 via a TR15. When a detector 1 is selected by the switch 3', the aural signal of the detector 1 emerges at the point P to be delivered to the terminal 16 via the TR15. In such constitution, the shock noise which is produced when changing over a selection switch can be eliminated. |
