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THREE_TONE_OSCILLATOR

2016-08-19 11:20  
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THREE_TONE_OSCILLATOR
This TTL tone oscillator can generate one of three tones. The tone generation depends on the status of the two input control lines. The design consists of two standard TTL audio tone oscillators merged together using one 7400 TTL chip. Two input lines control the output status. With both inputs low, no output is generated. When input A is high, the high-tone oscillator is gated on. When input B is high, the low-tone oscillator is gated on. With both A and B high, both oscillators are gated on and the output tone generated is midway between the high and low tones. The 1N914 diode in series with a 1-kΩ resistor imposes a 50-percent duty cycle on the waveform. A low-pass filter on the output removes harmonics and mellows the output tone.