Understanding the Operation of Modern Digital and Analog Uniphones: DAC, ADC and Power Supply

This "digital" intercom is not so digital. ADC and DAC are not there! The department is something like this:
The switchboard (as called, so called) sends calling pulses to all uniphones. The one whose number matches the number of pulses takes part in further communication that takes place analog in this "digital" equipment. How about power supply and two-wire conversation? Please refer to the diagram of the analog telephone.

I would like to add that often the power of unifoów when idle is turned off. When a cassette number is selected, the power is turned on. Then the internal circuits are reset (counter or microcontroller) and wait for pulses.
It can also be so (when the power is on all the time) that first a long pulse (reset) appears, then a short one, the number of which depends on the number selected on the cassette.
Pulse times are different and depend on the manufacturer of the cassette, although an unofficial standard has been created (Urmet, Cyfral).
How to check it all? Oscilloscope with memory or Saleae and the "partner" who will be at the cassette. Of course, it's best to buy a digital intercom kit and start your analysis. Then even our simple oscilloscope can be used.

As for fully analog intercoms (actually a bit digital, because, for example, in 5-wire one of the lines there is voltage or there is no voltage - calling), you can deduce from the diagram. In the case of intercoms with 4 or more wires, the principle of operation is very simple, with 2 wires it is not.

Analogs can be made on 2 wires, but a separate pair must be run to each premises. The digital ones can all be plugged into one pair. I have schematics for "digital" on 3 wires somewhere. The advantage of digital is that a badly hung up receiver does not block the entire system, as it is usually the case with analogs, especially on 4 or more wires.
Naturally, speech is transmitted as in analog telephony (as on the first telephone in the world). The cassette usually has a hands-free system (I don't remember the symbol, MC ??? 34 - I was doing the device on it, it suppresses the echo)

guciq wrote:

I install farfis intercoms and they are fully digital - each device has its own address. Even the image from the camera runs on 2 wires together with audio and power

Are you sure digitally?
Audio 20Hz ... 20kHz (speech 300Hz ... 3400Hz), video 0..4 (6) MHz, you can move beyond the audio and all analog. Give the documentation of these intercoms, etc., and you will know if they are analog or digital because I doubt. The cost of codecs, mixers etc. is not low.

Check the prices of some devices for audiophiles, and inside ... an ordinary device often with parameters worse than the middle class.
If the device does not have codecs, it is analog. Write down symbols / take a photo of key layouts.

Ircys wrote:

There are intercoms only conventionally called digital, such as ACO, Laskomex, Proel and fully digital intercoms. Some companies offer them, e.g. Bticino, Farfisa, Siedle, BPT, Comelit, etc.

This is what I want to prove @guciq.
It is possible to design an intercom via optical fiber, but why? Digital audio transmission? What will we gain apart from increasing the price? You have to give codecs. The problem of eliminating the anti-local effect is much greater than in the case of analog telephony. And if you look closely, the ISDN "modem" transmission itself is a bit more analog in DSL. In ISDN 2B + D we have a bit rate of 2x64kb times two directions + signaling. So the speech signal itself needs 256kb and the bit rate of such ISDN is only 114kb. How is this possible? 2B1Q coding, i.e. 2 bits coded in one time unit, which means that the voltage has four levels. There can be up to 256 of them in ADSL, because how else can you get a bit rate of 40MB in the 1MHz band?
VoIP. Let us assume that the data transmission itself is digital, but data packets, although having a CRC, are not retransmitted in the event of an error. The sound is divided into packages of 20, sometimes 30 ms and such a package may not deliver to the addressee. In ISDN it looks much better because individual bytes are lost. That is why VoIP has such problems with fax transmission that I will not mention modems. Sometimes even, due to compression, DTMF signaling does not pass!

guciq wrote:

In the Farfis duo (digital) system, each device has an address, and everything else goes in one pair

We've already established that this is also the case in pseudo-digital ones, so it's not an argument.

guciq wrote:

In theory, you can connect up to 20,000,000 users!

On one pair?

guciq wrote:

You can call up images from ordinary analog cameras. Intercom calls do not block connections. In the latest system, the intercom rings the cell phones and you can remotely open the gate or alley by pressing #.

Slican centrals do it too. It is true that they withdrew from analogue switchboards, but on NP NCT it could be realized with an analog intercom, analog telephones and analog GSM gateways. By adding a VoIP gateway (or Slicna digital exchange), you can implement these functions in this technology.

guciq wrote:

From the internal panel with a single button you can call a mobile phone (emergency) to help the elderly or children when something happens. Possibility of remote programming by sending codes from the installer's cell ... etc.
And you stay in the analog as you like

It sounds like an advertisement and not technical information. I am an unbeliever and I won't believe until I see. I wrote, documentation or photography.

guciq wrote:

Just have a look, for example, here: www.alpol.com.pl.
You have everything there - catalogs, manuals, etc.

I will look there, although I know that this is a waste of time, because producers do not put diagrams etc. on their websites, it is not Elektroda or EP or EdW. If anything, such things are available to authorized services.

Added after 3 [minutes]:

How do they sell it if the documentation for the client is not in Polish?

guciq wrote:

When you buy, you get Polish instructions

It's going to be fun. If you buy a pig in a poke, you will find out how dairy it is. Customer, under no circumstances are you entitled to read the instruction manual before purchasing (probably because he would not have bought it then). Intercoms only for foreigners. Interesting approach to the client.

guciq wrote:

Bdw English is almost a standard when it comes to electronics

So why is the Polish version of Win, Linux, instructions for TV, washing machine, etc.? Panasonics, Siemens, Rigol, Textornics not only provide Polish instructions but also menus on their devices! With them, the fire from intercoms falls out pale they break Polish law ! UOKiK should deal with them.

PS
I sent a question for codecs. I wonder if they will answer.