2-wire doorphones

nmacc

Hi folks,

Just wondering if anyone knows how 2-wire doorphones encode the audio & video?

I ask because I have encountered lots of 2-wire doorphone monitor units that have additional camera inputs. Several times I've wanted to use these, but all of the ones I have seen have been designed to accept input from either additional door units or else cameras from that specific manufacturer.

In other words the signals have to be encoded in the same format as the original door unit, so a regular composite video signal won't work (although I haven't tried this!).

I suspect that most of the manufacturers use a similar process, probably based on the same chips, but I don't know how this works or even if it's analogue or digital.

Can anyone enlighten me?

kub

Two different manufacturers come to my mind these are Comelit and Aiphone, both excellent brands, now there are others out there which I am sure are good but I have years of experience with the afore mentioned.

Closed protocol is your issue, so if you wanted a normal bog standard analogue to work with one of the above, it won't.
Each manufacturer make their own entire kits and have massive ranges of equipment to choose from so if you have a Comelit system then it's only a Comelit camera which will work on it, of course things like a particular range would also come into the mix.

I hope that helps.

nmacc

kub wrote: »

Each manufacturer make their own entire kits and have massive ranges of equipment to choose from so if you have a Comelit system then it's only a Comelit camera which will work on it, of course things like a particular range would also come into the mix.

I hope that helps.

Well er, no actually, it doesn't. You see I sort of knew all of the above; that was my reason for posting the question,

It is the nature of these things that someone more capable than I has already become curious enough to ask this question and has then found the answer. I suspect that if I could craft the correct search term that I could find an explanation on the steam internet.

Because there is so much of this kit around, especially from China, I'm sure someone knows what is compatible and if it's not, how to make it so.

kub

nmacc wrote: »

Well er, no actually, it doesn't. You see I sort of knew all of the above; that was my reason for posting the question,

It is the nature of these things that someone more capable than I has already become curious enough to ask this question and has then found the answer. I suspect that if I could craft the correct search term that I could find an explanation on the steam internet.

Because there is so much of this kit around, especially from China, I'm sure someone knows what is compatible and if it's not, how to make it so.

Ah my apologies, you are a lot more advanced than i had assumed.....we have cracked the different manufacturers analogue handset wiring, that is of no assistance to you though.

Being completely honest, as far as i am currently concerned an 2 wire Aiphone part will only work with another Aiphone part and likewise say with a Comelit.

Have i ever experimented....no, i suppose the simple reason is most of us on here are self employed and as i ma sure time id of the essence.

But having said that, if you can manage to work something out, please let us know.
Ps just if is of any assistance the Aiphone 2 wire equipment must be pushing on over 25 years in existence.......stone age digital technology perhaps

nmacc

kub wrote: »

A
Have i ever experimented....no, i suppose the simple reason is most of us on here are self employed and as i ma sure time id of the essence.

But having said that, if you can manage to work something out, please let us know.
Ps just if is of any assistance the Aiphone 2 wire equipment must be pushing on over 25 years in existence.......stone age digital technology perhaps

Similarly I have never had the time to look into these matters, however there seems to be a never-ending supply of folks - usually American - who have the time, equipment and skills to investigate such matters.

I would expect that the Chinese manufacturers may use similar systems to each other and these would turn up in the large amount of Chinese kit on the market and also OEM kit as used by Borsatec & others.

As for the Aiphone kit being around for so long, that was why I wondered if an analogue encoding system might be in use.

I'll let you know if I find anything.