| 摘要 |
PURPOSE:To attain ease of cancellation of registration on the way of registering operation of a telephone number as an abbreviated number by detecting that a specific pushbutton is depressed consecutively over twice. CONSTITUTION:Delay flip-flops (FF) 1, 2 change the state of an output Q in synchronizing with the trailing of a clock input C and both the FFs are connected in cascade as a binary counter. Every time a specific pushbutton is depressed, a pulse signal S is impressed as the clock input of the 1st FF1, and the FFs are connected so as to reset both the FFs 1, 2 by a pulse signal A generated any of numeric pushbuttons is depressed. When the numeric button is depressed while a specific pushbotton is depressed for twice or over, the FF is reset and when the specific pushbutton is depressed twice consecutively, the output Q of the 2nd FF2 is inverted to a high level and becomes a cancellation signal via a differentiation circuit 3 and outputted. |
