| 摘要 |
PURPOSE:To use one alarm for both key input and echo detection by driving the alarm by an OR circuit even from a key input and an echo detection side when a switch is connected and driving the alarm only by the key input when the switch is disconnected. CONSTITUTION:When an echo signal which is higher than a set level is present in a gate, an H-level signal is sent out of a detecting circuit to a terminal 5 and when the switch 2 is ON, the buzzer 30 sounds. When the switch is OFF, the buzzer does not sound. An MPU, on the other hand, controls the key input and when a key input state is detected, the MPU outputs the H-level signal to a terminal 8. Consequently, when the switch 2 is ON, an L-level signal is outputted as a Q output from a terminal (e) and the buzzer 30 sounds. Further, when the switch 2 is OFF, the MPU sends a driving signal to an FF1 on detecting the key input and the H-level signal is outputted as the Q output from the terminal (d) of the FF1 to make the buzzer 30 sound through the switch 2. Consequently, only one alarm is required. |
