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Dual Operation Amplifier Circuit

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waqar

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Using Phase-Shift type RC Oscillator theory iam trying to design a circuit which can generate DIAL TONE type of sound just like we hear in our normal telephone sets when it goes off-hook.

I have used KA1458 which is a dual op amps. I have used one op amp as RC oscillator and the 2nd one as buufer and supplied this op amp with -ve 5 volts and +5 Volts. Assuming the capacitor as 0.1uf i have worked the ressitor value using

Freuqency = 1/ 2*pi*R*C*under-root6. placing the frequency as 450 Hz.

The Dial tone which iam getting is not perfectly like the Dial tone which appears in normal telephone sets connected with PSTN. Is tehre any other way of generating Dial tone or suggest any adjustment in this schematic. Iam looking for the most economical solution.
 

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Skyknight

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Why isn't that tone perfect? I don't know if you are refering to the quality of the sound, buuut I know that frecuency is not 450Hz but 440Hz :wink: . I know that because it's the first musician trick when you have no tuner to tune your guitar strings up. The soung after picking up the phone is a natural LA (or, in american music language: a perfect A) You know C, D, E, F, G, A, B? Just the musical notes :D
 

waqar

New Member
using the same op amp for Busy, Ring back and Dial tone

can i use the same KA1458 to generate BUSY and RING back Tones...

IC like M-991 or MAX293 is not avaiable in my region..so i have make use of op amps...

any ideas from generating DIAL TONE (which is alreadyi have done using the above post schematic) , RING BACK and BUSY TONE...should i use 555 or this op amp can work in some otherway
 
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