How to Make a Dual Tone Siren Circuit
A free running or astable multivibrator is one which has two semi stable states and the yield of one stag is joined with the information of the other through a coupling capacitor.
Since both the states are semi stable, the yield accomplished is constantly changing in nature i.e. high, low high low-.
The yield is in the structure low heartbeats, the recurrence of which relies on upon the base biasing resistor and the coupling capacitor, When these resistances and condensers for both the stages are of diverse qualities, the yield ` wave structure is rectangular; this is on account of the time consistent of the two semi stable states gets to appear as something else.
On the off chance that this time steady of the two, states is made the same, the yield acquired then is square wave. Two conditions of the multivibrator are made indistinguishable by the utilization of the same estimations of segments.
The segments utilized as a part of the circuit (Fig). result in a square wave yield and the time steady chose is to give a genuinely decent ascent and fall of the siren.
In any case, one may change the benefit of coupling capacitors to get whatever other wanted time steady. The second unit is an oscillator area. The condenser associated at the yield is the input condenser. It decides the tone of the siren.
Higher the estimation of the condenser the lower is the pitch. for high pitch sound (by and large utilized as a part of siren) criticism condenser going from 0.047 uf to 0.1 mfd ought to be chosen. The speaker may be metallic case (horn sort) or little planer cone. The metallic cone horn gives better results.
Parts for dual tone siren circuit
R1,R2,R5,R6= 22K
R3,R4 = 2K2
R7 = 10 Ohms, 1 watt
C1,C2,C4 = 0.1uF
C3 = 22uF/25V
T1,T2 = BC557
T3 = BC547
T4 = 2N2907 or 8550
i only get a single tone, is there a common mistake im making
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