| 摘要 |
PURPOSE:To avoid useless display current when plural control means are operated at one time for a channel selecting circuit of a TV picture receiver, etc., by setting a current limiting resistance in series to a light emitting element for channel display. CONSTITUTION:The current supplied from a 32V power supply line 5 is limited to actuate a transistor TRQ4 at a moment when control switches S1 and S2 are operated at one time. At the same time, the current flowing into the 11th pin from the side of a light emitting diode D22 via the switches S2 and S1 is limited by current limiting resistances R22 and R21 and after a low level is set for the 11th pin 11 of a channel selecting IC circuit 1. Thus the light emitting diode is substantially turned off. In this case, the current flowing from the line 5 through a volume VR2 plus the switches S2 and S1 is also limited, and the channel selection state set previously may possibly vary mistakenly. However, a capacitor C5 functions to give no effect to the TRQ4 against the voltage rise at point (c) caused by the mistaken channel display current. Thus the display has no change. |
