| 摘要 |
The control circuit has a pair of input terminals and a pair of output terminals connected to the buzzer. A pair of flip-flop stages is used, for providing two different frequencies in alternation. The first flip-flop stage has two outputs with a positive and a ground potential respectively. Each is coupled to an input of the second flip-flop stage via a respective resistor (R4,R3). The second flip-flop stage has a series circuit with a capacitor (C2) and an inverter with a Schmitt trigger input (IC1-C). These are coupled in parallel with a series circuit of a resistor (R5) and a second inverter with a Schmitt trigger input (IC1-D), with a resistor coupled across the second series circuit. |
