| 摘要 |
PURPOSE:To prevent the radiation of the undesired electric waves and thus avoid the long-time press by starting the start circuit by the press of the press-to-talk switch for the extraordinary long period of time and then securing the transmission unable state via the latch circuit. CONSTITUTION:The 1st terminal of switch SW is earthed, and the 2nd terminal is connected to detector circuit 1 as well as to inverter 2. Here the press action is given to SW for a long time, and thus inter-terminal voltage EC of capacitor C is lowered down to voltage ES which gives start to start circuit 3. And circuit 3 is started by the press of the extraordinary long period of time and by setting previously the time constant to a proper level. With start of circuit 3, output Q' of latch circuit 4 changes from the high rank to the low rank. Then the ouput of AND circuit 5 features the low rank. Thus transistor Tr is turned off to secure the transmission unable state. As a result, the undesired radiation can be prevented for the electric waves, thus avoiding the long-time press. |
