| 摘要 |
PURPOSE:To simplify the construction of a push button, by replacing mechanical common contacts of the push button switch by the 1st, the 2nd and the 3rd switching elements, and obtaining an oscillation signal without chattering. CONSTITUTION:When the push button is depressed, a frequency contact 31 is activated, the information is detected at an oscillation circuit 32, an oscillation signal is outputted via a resistor 33, a depression signal is outputted from a control output terminal 34 and fed to a control input terminal 60 of a switch control circuit 6. A signal turning off a PNP transistor (TR)7 is outputted from the 1st output terminal 61 of a switch control circuit 6 to disconnect a channel circuit 5 from a line terminal 1. Simultaneously, a signal turning on an NPN TR8 is outputted from the 2nd output terminal 62 of the circuit 6, both end terminals of the channel circuit 5 are short-circuited and an oscillation signal from a resistor 33 is fed to a line terminal 2. Further, a signal turning on a NPN TR9 is outputted from the 3rd output terminal 63 of the circuit 6 to connect a resistor 10 in parallel with a resistor 4. |
