4 way intercom

[frozenrose_5234]

I want to make a 4 way intercom using only push buttons. Is that possible?

And there is a condition; if I (telephone 1) only want to talk to telephone 2 the other telephones 3 and 4 cannot hear our conversation, also if telephone 3 wants to join our conversation(telephone 1 and 2), telephone 4 cannot hear it.

Can you help me please

 

[4pyros]

Most intercoms will only allow a two way conversation. To get three or for selectible you would need some kind of switchboard. You could do it with a BPX telephone hook up.
Andy

 

[Sceadwian]

It could be done with only push buttons, but you'd need a lot of wires, and multiple speakers.

 

[Mr RB]

You can multi-station intercoms very easily if they all share the same line (all are in receive mode amplifying anything on that same line).

Then they have a push-to-talk button that lets each intercom station transmit a signal onto the shared line, and the push button also stops that station from listening to the line as it transmits (to stop feedback) or simply attenuates it's listening amp while it transmits. It was a pretty common system in the old days of office and workplace intercoms.

The only issue you have is how to STOP stations from listening in. The only easy way to do that is locally, so each station itself can be turned off when not in use. Anything more complex than that is difficult as you need a way for stations to turn off other stations or a master system (like a switchboard) that can turn any stations off.

 

[Boncuk]

There are conference amplifiers on the market like the CPA5200.

Not sure if it will meet your requirements.

You might also look around on air plane wrecking lots and search for conference amplifiers built into transport planes.

Boncuk

 

[moicez]

you could use AM (amplitude modulation) or any other modulation. Each telephone would have its own frequency, so if you want to send for example a message for phone1 from phone2 you only make phone2 transmit the signal at its frequency. You would have to put filters on all phones for its particular freq.

 

[Sceadwian]

moicez, you can't AM modulate with just push buttons..

 

[moicez]

moicez, you can't AM modulate with just push buttons..

Why not? It's kinda experimental I get that. What I'm thinking is that the interface would have 4 buttons so you can communicate with the desire phone#. Those buttons can enable/disable parts of the circuit that transmit the proper frequencies.

 

[Sceadwian]

And the circuit that would enable it to exist would be more complicated than the push buttons requested. This is not my idea moicez, nor is it yours. You and I should be here to help other users realize THEIR goals. If we can't do that, politely suggest alternatives. But with a pre-requisite of physical switches, adding AM modulate is not a solution.

 

[moicez]

Well my idea could work the way frozenrose_5234 wants to: "And there is a condition; if I (telephone 1) only want to talk to telephone 2 the other telephones 3 and 4 cannot hear our conversation, also if telephone 3 wants to join our conversation(telephone 1 and 2), telephone 4 cannot hear it.".


But the other idea is boring and you need LOTS of wire, you probably wont learn anything

you'd need a lot of wires, and multiple speakers

I really don't see anything wrong with my original post, it does resolve the problem. You only need 4 oscillators being modulated, 1 amplifier and 4 envelope detectors (easy) per device.

 

[4pyros]

Give it up the OP has not been back since his origanal post.

 

[moicez]

Give it up the OP has not been back since his origanal post.

Maybe someone will find the info useful.