The integrated circuit U1 is configured as a low-frequency asymmetrical oscillator. Its output is inverted by Q1 and sent to the reset terminal of U2 at pin 5. Integrated circuit U2 operates as an audio oscillator and is activated when the output of U1 is low. With the voltage at pin 5 of U2 held constant, the circuit produces a "bleep" sound. The voltage across capacitor C1 is directed to the base of Q2, which activates it and grounds pin 5 of U2. As the frequency of the reset signal on pin 4 decreases, the output frequency of U2 increases, resulting in a "whoop" sound that starts at a low frequency and transitions to a higher frequency. Resistor R1 establishes the repetition rate, while R2 controls the duration of the whoop. Resistors R3 and R4 set the center operating frequency.
The circuit described comprises two integrated circuits, U1 and U2, working in conjunction to produce audio signals characterized by distinct frequency patterns. The configuration of U1 as a low-frequency asymmetrical oscillator allows it to generate a square wave output, which is inverted by transistor Q1. This inverted output serves as a reset signal for U2, ensuring that U2 operates only when U1's output is low.
U2 is designed as an audio oscillator, which generates sound waves based on the input it receives. The activation of U2 occurs when the output from U1 transitions to a low state, allowing for consistent audio generation. The constant voltage at pin 5 of U2 ensures that the oscillator remains stable, producing a "bleep" sound until the reset condition changes.
Capacitor C1 plays a crucial role in controlling the timing of the circuit. The voltage across C1 is fed to the base of transistor Q2, which functions as a switch. When Q2 is turned on, it grounds pin 5 of U2, effectively resetting the oscillator. This interaction between U1 and U2 leads to a dynamic change in the output frequency of U2. As the reset signal frequency at pin 4 decreases, U2's output frequency rises, producing a "whoop" sound that varies from low to high frequency.
The resistors in this circuit are essential for defining the characteristics of the output sound. Resistor R1 determines the repetition rate of the audio output, effectively controlling how often the circuit produces sound events. Resistor R2 is responsible for adjusting the duration of the "whoop," allowing for customization of how long the sound is sustained. Resistors R3 and R4 set the center operating frequency of the audio oscillator, fine-tuning the sound produced to meet specific design requirements.
Overall, this circuit configuration provides a versatile means of generating audio signals with varying characteristics, suitable for applications in alarms, alerts, or other sound-producing devices. Integrated circuit Ul is connected as a low-frequency asymmetrical oscillator. Its output is inverted by Ql and fed to the reset te rminal of U2 at pin 5. Integrated circuit U2 is configured as an audio oscillator and is enabled when the output of Ul is low. With the voltage at pin 5 of U2 constant, the circuit just" "bleeps."" The voltage across capacitor CI is fed to the base of Q2, which turns it on and grounds pin 5 of U2.
When the frequency of the reset signal on pin 4 falls, the output frequency of U2 rises. The output then becomes a whoop, starting low in frequency and ending high. Resistor Rl sets the repetition rate and R2 determines the time duration of the whoop. Resistors R3 and R4 set the center-operating frequency.
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