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Wailing Alarm Siren

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Wailing Alarm Siren by Tony van Roon Parts List: R1,R5 = 4.7K C1,C4 = 100uF/25V, electrolytic R2 = 47K C2,C3 = 0.01uF (10nF), ceramic R3 = 10K T1 = 2N3702 (NTE159, TUP, etc.) R4 = 100K IC1,IC2 = LM/NE555, MC1455P, etc Rx = *Notes LS = Loudspeaker. *Notes Notes: This circuit provides a warbling sound to any alarm circuit. IC2 is wired as a low frequency astable with a cycle period of about 6 seconds. The slowly varying ramp waveform at C1 is fed to pnp emitter follower T1, and is then used to frequency modulate alarm generator IC1 via R6. IC1 has a natural center frequency of about 800Hz. Circuit action is such that the alarm output signal starts at a low frequency, rises for 3 seconds to a high frequency, then falls over 3 seconds to a low frequency again, and so on. *The Loudspeaker LS and the resistor marked "Rx" should be together 75 ohms. If you have a standard 8-ohm speaker then Rx is 67 ohms. ...read more.


This varying voltage modulates the frequency of the 2nd IC. This process repeats and what you hear is the sound remarkably similar to the police siren. Two presets VR1 and VR2 are provided to vary the siren period of repetition and the tone of the siren. By varying VR1 you can set how fast the siren changes from high freq. to low freq. VR2 sets the siren frequency. Adjust VR1 and VR2 to suit your taste. External Bellbox Siren/Strobe � Fully self-contained � Extremely loud 114dB piezo sounder � High intensity flashing blue strobe light � Selectable SAB mode or SCB mode � Built-in NiCad backup battery � Adjustable sounder cut-off timer � Flashing comfort LEDs � Robust polycarbonate construction � Protective inner skin � Dual tamper switch protected An attractively styled, external siren box with integral blue strobe light. Fully self-contained, the unit has an adjustable siren cut-off timer and is supplied with comprehensive instructions on connecting to all the most popular alarm panels, a mounting template and fixing screws and wall plugs. ...read more.


Tamper � 3 Part-set programs � Easy to programme An eight-zone fully programmable hardwired alarm kit for use in domestic or small commercial properties. The system features a remote keypad (RKP) that allows the main panel to be hidden away making for a much neater installation. The kit includes all the security components necessary, including step by step installation instructions. The system can be expanded to include up to four remote keypads and a wide range of additional detectors. `` Big Ben Sound This circuit produces the famous Big Ben sound. It produces the "ding dong" sound when switched ON. Basically the circuit alternates between two frequencies which are adjustable. This produces the "ding-dong" sound. The first IC(left) oscillates at about 1Hz. The second IC's tone is modulated by the changing voltage at the output of the first IC. The first IC determines how fast the changeover from one frequency to the other takes place and second IC determines the tone of the final output. By varying the VR1, the changeover rate can be adjusted. By varying VR2 the tone can be adjusted ...read more.

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