20Hz signal generator (phone-ringing) circuit diagram

As shown for the 20Hz signal generator, may be applied to the telephone ringing system, the signal source can also be used for alarm systems and other electronic Used. The circuit is actually a transformer T and a transistor VTl, VT2 composition

of total fat push-pull oscillator, two transistors working in the off state (saturation and cut-off), the output waveform is a square wave. Transistor low power consumption and high efficiency.Component selection: transistor VTl, VT2: 3DD4E, = 30 ~ 80 (parameter selection as consistent). Radiator area l00 50mm2, aluminum plate having a thickness of 2mm. Oscillation transformer T: using E-type silicon material, core cross-sectional area of 35 22mm2. Ll-3: µ0.49mm high strength wire, wound 189 turns. L4-6: µ0.25mm high strength wire, wound 40 turns, and all around the center wire taps. L7-8: µ0.35mm high strength wire, wound 60 turns. Choke coil L: using E-type silicon material, core cross-sectional area of 20 15mm2. L: µ0.55mm high strength wire, wound 800 turns. Resistor nominal power are selected 1 / 2W metal film resistors. Other component values as shown in the figure, no special requirements.

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