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wireless intercom

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pls I need a circuit diagram for 5watt and 80m or 100m wireless intercom for room to door communication or office to office communication . I am HND Electrical Elctronics Engneering student from Nigeria.
 
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You're going to have to give us more than that.

What are your requirements? What is your experience level? Where are you located (so we know where to send you for parts)?

You're not going to get an in-depth answer if you only ask an extremely vague question.
 
I just need a simple circuitry.

Well we just need simple requirements. What KIND of intercom?

If you don't give us something helpful to go on, you're not going to get any helpful answers.
 
A wired intercom can be simple for us because we are experienced but it will be very difficult for you.
A wireless intercom has two complicated radio transmitters and two complicated radio receivers in addition to the wired intercom parts. You probably will not be able to make it work.
 
Muili Ibrahim Babatunde , you're not helping. This thread will not go anywhere if you don't explain exactly what you're looking for, what your experience level is, and so on.
 
My experience level already have been mentioned.

You mentioned you were a student. You did not say what year, nor how much actual circuit experience you have.

I am student looking for transmitter and receiver circuitry for wireless intercom.

Is this a school project then? Have you tried googling "wireless intercom schematic"? You should always start off with Google--it can be your best friend.
 
In Google I found a wireless intercom schematic. It is very complicated. It uses 30MHz FM for its audio but it uses old fashioned "voice switching".
Voice switching is when I talk then you hear me only if you are completely quiet with no background sounds. I hear you talk only if I am completely quiet with no background sounds. There is only one radio audio path at a time.
We keep cutting off each other and background sounds also cut us off. Most wired intercoms also have this problem. Most handsfree speakerphones also have this problem.

Maybe there is a complicated wireless intercom for a glass window that uses two modulated infrared paths for the audio? But since it needs a wired power supply then why doesn't it use simple wires for the audio paths?

Maybe it can be done with bluetooth transmissions? Nice and complicated.

When using two audio paths, how would you prevent acoustical feedback howling where a sound goes in my mic, out your speaker then into your mic and out my speaker then in my mic again ..... and the sound goes around and around.
Maybe the acoustical feedback can be prevented with a nice complicated digital echo canceller circuit?
Polycom speakerphones use a digital echo canceller circuit so the voice path does not switch and you do not get cutoff. Check their very high prices.

I think the student is learning how to solder, not to design a circuit nor understand how it works. He/she should select a simple circuit.
 
Don't use a wireless system.
Make a simple carbon button mic telephone system.
Requires 2 wires or even one if you use a water pipe system for one wire.
Can run on batteries.
 
2 ordinary telephones and a dc power source, you could add a third wire for a call button and buzzer.
 
He wants to make an intercom system, not a telephone system.
An intercom has a loudspeaker at each end to produce acoustical feedback howling when it is designed wrong. But there is one at www.RedCircuits.com that cancels your voice from playing in your speaker, see my attachment.
A cheapo intercom system has a push-to-talk button that disconnects your speaker to avoid feedback howling.
A low cost but not cheap intercom system uses voice-switching that gets messed up if there is background noise. It also cuts off voices.
 

Attachments

  • Intercom full duplex.gif
    Intercom full duplex.gif
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Yes, that is what he said he wanted.
He might be happy with a simple system that allows communication.

A two wire system is possible, with buzzer, if you use a spdt switch at both ends.
Telephone Circuit.png
 
Looking at my post above, the schematic, I think I see a flaw. Not sure.
I'm thinking if two of these are connected the batteries cancel each other out leaving a net voltage of 0 volts.
The system will not work.
Is this correct?
Perhaps the solution is to reverse one set of the batteries.
The buzzers won't care but if they are piezo sounders one will have to be reversed too.
 
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An old fashioned carbon microphone needs a battery. A modern electret mic also needs to be powered but it needs a preamp.
So your schematic does not make sense.
 
A carbon mic and magnetic earpiece in a telephone handset are extremely old.
Isn't this thread about loudspeaking intercoms?

Many years ago (1982?) I made a speakerphone that used a Motorola voice switching IC that worked very well. Two can be used as an intercom.
 
Perhaps my post should be in another thread.
Sure it's an old system. I imagine you could still find these hand sets.
The OP has disappeared and my solution was very simple and something he may have been able to build.

When I was eleven years old I built two of these sets in cigar boxes and installed one in a house four doors away.
I used one wire along a backyard fence with the neighbors permission and the water system for the other wire.
It had hum but it worked. I don't think I had to reverse one set of batteries.
I'd still like an answer to my question above in post #15 please.

BTW, the girl had no interest in me and only answered the phone once :)
 
When I was 11 I didn't simply phone the neighbour girl, instead I met with her and we did homework together.
Yes, the battery and piezo beeper in one of your old phones must have the polarity reversed.
 
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