Red Alert Star Trek Alarm Siren, #1

Red Alert Alarm, Schematic

Parts List:R1,R4 = 10KC1 = 10uF/25V, electrolytic R2 = 75KC2,C3,C4 = 0.01uF (10nF), ceramic R3 = 1K C5 = 470uF/25V, electrolytic R5 = 100KIC1,IC2 = 555 Timer/Oscillator Q1 = 2N3055 D1,D3,D4 = 1N4001 LS = Loudspeaker, 8 ohm D2 = 1N4148	

The circuit above provides a ’pulse-tone’, like the one you know from the old Star Trek.The output stage contains a power-booster with Q1 (2N3055), providing several watts to the loudspeaker SPKR1.
Clamping diodes are used to limit the speaker’s inductive kickback to a safe level.To prevent the output signal from feeding back into the 555’s via the supply line, the supply lines are filtered by a capacitor and an isolating diode (C5 and D2).
This circuit acts as a pulsed-tone alarm-call generator.Integrated circuit U1 acts as an 800-Hz tone generator, and is gated on and off once per second by U2 via D1.

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