- Freddy Dopfel
Living a Keyless Life
Keys suck. I could write a whole post about how easy they are to copy (even with just a photo) or circumvent altogether. However, this post focuses on another problem with keys: they are inconvenient.
I strongly believe that we should live in a world where machines anticipate our needs and respond to them before we even have to ask. In my home, lights turn off when I leave and on when I arrive, security systems automatically arm and disarm themselves, robots vacuum the floor, clean the air, wash the dishes, and monitor my sleep to slowly wake me up and prepare my morning tea.
So why is it that every time I go through a door, I should have to put down whatever I am holding and shuffle around in my pockets for a few seconds to find keys? Why must I stick a small piece of metal in a lock and twist it to gain access to my own home? Shouldn't these doors recognize me and let me in automatically? And furthermore, why should I have to carry a bunch of pointy pieces of metal in my pocket, so that they can dig into my skin and my clothes and scratch my gadgets? The entire system is barbaric!
So after I removed car keys form my life through the Tesla mobile app, I decided I wanted to remove house keys from my life as well, and then finally be completely keyless. I am a renter in an apartment building, so my options for renovation are much more limited than if I was living in my own house. I need to make sure that all my changes are reversible when I eventually move out: challenge accepted!
The door to my apartment was an easy fix. All I had to do was install an August door lock on my deadbolt and configure it lock and unlock when I arrive and leave home. Piece of cake. However, access to my building is restricted by an old-school intercom system. This would be harder. A little bit of disassembly revealed that the phone/endpoint terminal connects to the main control console through only two wires, like a phone.
My plan was to use a multimeter to record the signals sent to the command unit through those two wires when someone was granted access, and then emulate those signals with an internet connected Arduino. That way, the door to the apartment lobby could open whenever I instructed the Arduino to open it (AKA as I approached the lobby door).
However, I noticed an interesting marking on part of the PCB: "Cut here for doctor call"
Digging through various online manuals (I was unable to find my exact model's manual), I discovered that "Doctor Call" is a function that allows the door to automatically open when called without the user needing to pick up the phone (presumably to allow a doctor into the room of a patient in an emergency). I decided that enabling this feature would be a more elegant solution than ripping the phone system out of the wall and replacing it with an Arduino. This means that I would still have to press a button to gain access to my building, but at least I didn't have to carry a key.
I snipped the contact, but the doctor call mode wasn't working. Searching through manuals, it seemed that a button had to be pressed and held for a few seconds to enable doctor mode, but pressing the two buttons on the PCB didn't enable it. Strange.
Fearing that this was somehow broken, I decided to grab my multimeter, but I had a strange idea: As a last-ditch attempt, I decided to short (via the circuit board) the buttons installed on the board and those slots where buttons were not installed. Success!
I am not 100% certain why this worked, but my guess is that either one of these old existing buttons broke from many years of use (this is an old apartment, after all) or that the manufacturer chose to simply not install the buttons to turn on this feature as a cost-effective way of disabling it without having to design an entirely new intercom PCB. Either way, I can now live my life 100% keyless!