Cant find a simple push to talk intercom

Dodgydave

Joined Jun 22, 2012
9,316
Dodgydave, where do you get the "talk/listen" switch? Is it a self-centering switch with "talk" on one side, "listen" on the other side, and "no connection" in the center? That would not work. You don't want to have to hold the switch in the "listen" position to listen. What kind of switch is this creature?
It's a Dpdt latching in listen mode...
 

brockrwood

Joined Oct 23, 2016
47
In the old days, you could buy one of these and assemble it yourself. I did:

I miss the olden days. I criticized the “Shack” as it morphed into just another cell phone store. Still, I miss being able to run down to my local Radio Shack and get a part the lack of which was stopping my project from getting completed.
 

ian field

Joined Oct 27, 2012
6,539
Hi again

For some time now I have been in need of an intercom/PA system type circuit where I can have a button and mic in our lounge and run wires to a speaker circuit in our kids bedroom, with the purpose of preventing one of us having to continually run to the room telling the kids to behave or that dinner is ready. We have used a two way office intercom thing bought from ebay https://www.ebay.co.uk/itm/Home-Office-House-Flat-2-Station-Wall-Desk-Door-Intercom-with-Call-Chime-P152DA/253831404561?epid=8004528952&hash=item3b1987dc11:g:aCUAAOSwJ4hY~fFg for a while but it has developed bad interference to the point its unusable.

I done a search on AAC and came across a lot about intercoms but it can be quite confusing finding the correct circuit for my specific needs.
I came across this posted by dodgedave in a separate thread relating to intercom

can I ask would this basic circuit suit my needs, if so how far could the mic and speaker be separated maintaining good working and what kind of output does this circuit have is it clear -ish or have any kind of volume

If one of yous clued up doods could advice me on this or of a better circuit It would help me a lot.

cheers
There's a circuit in most versions of the Philips EE kits - there was an archive of scanned instruction manuals. Searching "Philips EE20" usually finds it. The older kits used germanium transistors, so PNP variants are also available. https://ee.old.no/library/
 

dendad

Joined Feb 20, 2016
3,595
I miss the olden days. I criticized the “Shack” as it morphed into just another cell phone store. Still, I miss being able to run down to my local Radio Shack and get a part the lack of which was stopping my project from getting completed.
Here in Oz it was branded "Tandy" and they had some really neat stuff, including those intercoms. In my town we are fortunate to have a Jaycar store and they have a pretty good range.

I had a Tandy intercom as above, and some power line carrier ones too. Are those types still around?
 

brockrwood

Joined Oct 23, 2016
47
Here in Oz it was branded "Tandy" and they had some really neat stuff, including those intercoms. In my town we are fortunate to have a Jaycar store and they have a pretty good range.

I had a Tandy intercom as above, and some power line carrier ones too. Are those types still around?
Love Jaycar! I wish shipping to the USA was more affordable. :-(

Speaking of Oz, Mr. Colin Mitchell has a great website down there in Australia called "talkingelectronics.com". You probably know this already, but he has hundreds of circuits and circuit ideas all available for free perusal on his website. I love his website when I want to get ideas for my next hobby project. I need to send him a thank-you note for the great website.
 

brockrwood

Joined Oct 23, 2016
47
I had a Tandy intercom as above, and some power line carrier ones too. Are those types still around?
Don't know about the power line-based intercoms. Never used one. It seems like a good idea. Wouldn't the 50 or 60 Hz AC hum on the power line be dreadful for sound quality?
 

dendad

Joined Feb 20, 2016
3,595
Don't know about the power line-based intercoms. Never used one. It seems like a good idea. Wouldn't the 50 or 60 Hz AC hum on the power line be dreadful for sound quality?
No, they are just low power FM "radio" transceivers using the power lines as the connecting media. I forget the frequency they operate on, but it is not very high. These intercoms are pretty handy and work quite well as long as they are on the same phase.
 

AnalogKid

Joined Aug 1, 2013
8,540
I have some in both AM and FM. The AM ones never have drifted over time, but of course are much more noisy. The FM ones are so quiet you can leave them on continuously as a room monitor, but they wander off over time. If you don't know how to align a low frequency FM receiver (agree, around 200 kHz) without a schematic, the only option is to replace.

ak
 
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Danko

Joined Nov 22, 2017
969
My own design. Works from 1.5V battery up to 10 km, using one wire (instead second wire of line used ground).
Two identical items. Push to talk.
No power ON/OFF button.
Listening item becomes powered automatically, when other item is talking.
28 Ohm loudspeaker aka microphone.

upload_2019-4-3_14-24-41.png
 
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