intercom "hack"

[Dublimax]

I want to be able to open the gate of the gated car parking where I live as I lost the swap card. I can open it for visitors from my apartment by answering the intercom and pressing a button. I want to be able to dial my apartment number to open the gate without anyone in my apartment.

I opened my intercom handset. See pictures attached.

To open the gate when someone buzzes I have to hang on which makes C and D go from D connected to nothing and C connected to pin 2 to C connected to 1 and D connected to 3(how they are on the picture). Once I have hanged on I press a button which pushes A on the right hand side of the picture 2, that makes connection with B.

I am a mechanical engineer and very bad at electronics but here is my idea:

My idea was to take the signal from the microphone (AC signal I guess), convert it to a a DC signal with a diode and a condenser (no idea about the values). This signal could activate a little solid state relay that would connect C and D to pins 1 and 3 to simulate that someone hanged on. The solid state would also connect D to B.

The problem I see by doing it this way is that C would still be connected to pin 2 whereas it shouldn't (is that a problem?).
I also have no clue about what condenser, diode to use and if I need any other components. Or even if my idea is good.

I would appreciate any help.
Thanks

 

[tpetar]

Re: intercom "hack"

I will make one button door entry code lock with password. Its simple circuit which have one button to enter code, each digit is represented with adequate button pressing (for example for number three, press button three times). Code have 4 numbers, if successful circuit activate relay which shorts button to open gate. Code entry button of this circuit can be replaced with transistor/optocoupler which is activated by optocoupler which pickup intercom buzzer/ring signal.


Here you can see one example of this device/circuit:
Button Code – Single Button Code Entry System
**broken link removed**


Best regards,
Peter

 

[Dublimax]

Re: intercom "hack"

Thanks for answering Peter.
It seems interesting but I was hoping for something a little bit simplier.
At this stage what I would need is to know how to modify the existing circuit to simulate the hang on and button push while still being able to use the intercom normally.
Thanks

- - - Updated - - -

Actually here is what I have in mind using a 4 pole SSR.
S1 is a manual switch that allows me to answer the intercom when I am at home (and deactivate the automatic system)
S2 is a manual switch that allows me to manually open the gate when I am at home
When noone is at home both S1 and S2 would be closed to allow for the automatic system to work.

How does that look?