That circuit will not work. Changed now to TL084? Maybe answer some questions about the project if you want help.

 

I am not familiar with the opamp originally used. And it is entirely possible that there is an error, either in the circuit as built or in the connection between the two. In fact, given the statement that the sound is only heard on the original circuit's speaker, that is proof that the circuit is not adjusted correctly.

So here is a question for the TS: Did you adjust the circuits according to the adjustment process described with the circuit??
Do you understand how the circuit is intended to function???

 

c

I am not familiar with the opamp originally used. And it is entirely possible that there is an error, either in the circuit as built or in the connection between the two. In fact, given the statement that the sound is only heard on the original circuit's speaker, that is proof that the circuit is not adjusted correctly.

So here is a question for the TS: Did you adjust the circuits according to the adjustment process described with the circuit??
Do you understand how the circuit is intended to function???

can u tell me that which preamplifier i have to use in both mic and speaker ?
can u give me circuit for preamplifier?

 

Until the circuit is adjusted correctly, it can not work as intended. AND, if the TS does not understand that, there is no point in considering adding pre-amplifiers.
So aquestion for the Thread Starter: Do you understand how the circuit is designed to function?? AND, have you adjusted it??

 

Until the circuit is adjusted correctly, it can not work as intended. AND, if the TS does not understand that, there is no point in considering adding pre-amplifiers.
So aquestion for the Thread Starter: Do you understand how the circuit is designed to function?? AND, have you adjusted it??

can u explain in easey language pleace sir

 

can u explain in easey language pleace sir

OK, here is an attempt to explain how that sort of what would be called a "full duplex" intercom circuit operates. The difficult part is that the actual circuit is not handy to provide the specific components involved. That is the circuit shown in post #14.
But here is a description of what is happening: The signal from the microphone is amplified to a level high enough to overcome the losses and noise in the connection between the two circuits. It is coupled to the other unit thru the resistor R11. The voltage developed across R11 is also fed to a complex subtraction circuit composed first of op-amps U1A and U2B, where the actual subtraction happens in U2C. The section R9, RV1, R10, and C3 are intended to simulate the reactance of the connection cable and second unit so that opposite signals can be amplified in the next stage, with the three opamps connected exactly like an "instrument amplifier". The function of that portion of the circuit is to amplify only the difference voltage between the two inputs, and totally reject the portion of the signal that is the same (common mode) of the two inputs.

One serious fault of that drawing is that the device number given is for the TL084 QUAD OPAMP package while the connections shown are for TWO PACKAGES of an TL082 dual opamp device.

So while the theory of operation is correct, the presentation is faulty. In addition, no circuit stage to drive an intercom speaker is given.
The bad news is that this circuit, as presented, is not really suitable for a beginner in electronics. And with no explanation of how it needs to be adjusted, how can it be expected to work??

The correct adjustment, will be when the variable resistor, RV1, and the variable capacitor, C3, are adjusted so that none of the input signal at J1A (audio In) is present at the audio output, J1B.

Where did the circuit come from??

 

Where did the circuit come from??
=its given from my senior of department


One serious fault of that drawing is that the device number given is for the TL084 QUAD OPAMP package while the connections shown are for TWO PACKAGES of an TL082 dual opamp device.
= sir iaam using LM6144 ic its ok or i have to change it or not

 

But here is a description of what is happening: The signal from the microphone is amplified to a level high enough to overcome the losses and noise in the connection between the two circuits. It is coupled to the other unit thru the resistor R11. The voltage developed across R11 is also fed to a complex subtraction circuit composed first of op-amps U1A and U2B, where the actual subtraction happens in U2C. The section R9, RV1, R10, and C3 are intended to simulate the reactance of the connection cable and second unit so that opposite signals can be amplified in the next stage, with the three opamps connected exactly like an "instrument amplifier". The function of that portion of the circuit is to amplify only the difference voltage between the two inputs, and totally reject the portion of the signal that is the same (common mode) of the two inputs.

=yes sir its noice cancllection intercom i know that , first i was maked simple intercom in that noice was transfering from one circuit to another but theri was loot of noice to stop that noice my sineor sir given me new circuit .
sir i relley have too made this project .
if you have any another circuit that you know it will work 100% please share to me please
it should we noice cancllection intercom .
and also one thing more we not have connect any hook switch or any another switch .

please hepl me sir

 

Other than the confusion of the device number I see nothing wrong with the circuit as presented. What I do sense is that if the TS is getting the input audio at the output connector, that either the balance has not been adjusted or there is a connection error. Certainly a less experienced person will find a challenge because of the confusing opamp notations. I will need to investigate the LM6144 device, as I am not at all familiar with it.

 

It's a rookie mistake with the circuit, no PhD required. As I said it cannot work, with any op-amp.
I'd give the answer but TS is keeping us in the dark ignoring our questions, which disrespects us all.
It seems to be telephone handsets with a carbon mic?

 

what that short forms meaning of [ PhD ] AND [ TS ] can u explain

 

Hi sami,
PhD is an Educational Degree and TS is Thread Starter, that is you.

E

 

I just read the data sheet for the LM6144! It is a rail to rail 17 MEGAHERTZ , low-voltage capable, very special, op-amp. My guess is that it was a free evaluation sample. The high frequency capability and enhanced slew rate make an adequate physical circuit layout mandatory, to avoid oscillation and instability. An LM324 or TL084, or similar, would be a better choice for an intercom system.
In addition the Thread Starter, (TS), has not even acknowledged the requirement for adjustment that I have repeatedly requested.

So either there is a very serious language gap or the TS is clueless about what we are discussing. Or simply wants a magical solution. FOR WHICH COMMERCIAL FEES ARE REQUIRED!!!

"PhD" is short for "Doctor of Philosophy" in some subject. It is the common highest advanced educational degree in some subject. In this case, electronics, it would typically require at least two more years of college work after a normal college degree. The normal interpretation is that itis an individual who understands everything in some area of knowledge.