Controlling ancient 4 wire apartment buzzer (un-lock only)

Ever since I moved into my co-op I wanted a way to upgrade the existing 4 wire apartment buzzer / intercom system to allow the outside door to be unlocked with my phone. I pulled the trigger on the SmartThings hub and a few add ons and I was thinking of ways to integrate the two together.

The device I was considering to make this possible is a Linear FS20Z-1

and I was looking to combine it with this:

I’m not an electrician but when I took the panel off it appears to be a 12v and three other wires, each one triggering an action using a momentary push button. What I’d like to do is wire in the Linear device which seems easy enough, power ground and neutral (which I’ll get from an outlet and a hacked PC power cord, then using the two “blue” wires, create a jumper from the 12v to the “door” button. Seems that the circuit will handle low voltage just fine from what I’m reading and it’s a simple normally open connection.

The app side of it seems simple, just a button to turn on the switch, put in a 5 second delay, and turn it back off.

Has anyone done something like this before? Do I have my thinking correct?


This is a genious idea!!!

I think this should work for you. All the button does is complete a circuit. So completing the circuit with a momentary switch = same thing as using the button.

Excellent… Just ordered the switch. My hub isn’t even in yet but should be arriving today… I can’t wait to get started. Should be useful not just for letting myself in but guests, my buzzer is right at the front door, it’ll be nice to not have to run across the apartment to let someone in. I’ll need to eventually combine this with a Yale deadbolt so I can not only get in the building but also my apartment with one button.

1 Like

Plus you could let someone in remotely!! :slight_smile: So thats cool!

Glad to have ya here man! Welcome! You should introduce yourself in the newcomers area!

Yeah I’ll pop in there later. Good idea on letting someone in totally remotely, easier than creating additional key codes.

1 Like

So I’m happy to report this worked exactly as expected. Right now I have an “energy saver” app tied to the switch so it will turn off after a minute no matter what… I’d prefer 30 seconds or so but I was limited to 1 minute being the minimum. I would like to do something a little fancier than turning it on then manually turning it off a few seconds later, I didn’t see where I could do that. Seems like it’s possible, just need to get a little more familiar with the software.

1 Like

Change the the relay to this:

It will work the same as a garage door opener relay and will only activate for a few seconds.

1 Like

I have the same tektone intercom system in my building. I was hoping to figure out a simpler way to have the door unlock automatically when someone pushes the button for my apartment. Not a secure option, I know, but this is necessary for my particular situation.I’ve heard that it can be done. Anyone know exactly what I need and how to do it?? Any help would be appreciated (in lay terms please as I am completely unfamiliar with this stuff!)


Wondering if you can put a simple YouTube video together showing what you did? If not an update as to how this setup is going. Thanks


I was very excited to find this post online because I wanted to do the exact same thing in order to facilitate using airbnb in my apartment, but I didn’t know exactly how to do it. I have the exact same relay switch and apartment buzzer, and I followed the instructions exacrtly (down to wiring the z-wave device up to power using an old computer cable :))

However, when I plug everything in, the door buzzer stops working. After taking the voltage between the ground and the door buzzer line, which should normally read 12 v (it drops to around 3 or 4 v when the button is pressed), it now reads 0. this indicates that the two blue terminals appear to be short-circuited.

Am I missing somethimg? I would have thought that as long as the switch is open, the voltage across the ground and buzzer terminals should remain at 12. and then when the switch is closed (turned on), it should short circuit (and voltage goes to 0).

Is there something wrong with my setup, or do I not understand how this device works?



Hi @Paullintilhac,

Did you wire the 2 blue wires to the button directly? You need to test which leads on the button are active when you are buzzing someone in at the main entrance.

Imosenko, thank you for your reply! I did not wire them directly to the button. What I did is connected one blue wire to the “door opening” wire and the other to the neutral wire, as described in the post above. I also justified this because I noticed the voltage between these two wires is ~24v, until the door button is pressed when it goes to 0v. I can double check the diagram for my buzzer and post it here for further clarification.

However, this still wouldn’t answer my question of why the voltage between the two blue wires is 0 as soon as I plug it into power? I thought the voltage would remain unchanged from the regular circuit until the switch is activated, and only then would it go to 0. Is that incorrect?

The Blue wires don’t conduct power until the circuit is closed. And if you set the relay as a momentary switch Type in ST IDE, it will only press for a second or so. This if you remotely activate it, the buzzer will turn on and off right away. I would recommend to wire directly in line with the button on your buzzer. This way the circuit is closed from that point and does not break any other circuitry.

Hi Imosenko,
Ok, that was my understanding. Which is why it is confusing how it appears to be conducting between the terminals as soon as I turn the power on. By the way, I have not yet actually set it up in smartthings – is it possible that the default position is closed? That would be very strange…

Here is a picture of the circuit diagram.

The power appears to be coming from terminal 2, as there is a voltage difference between this and all other terminals when no buttons are pressed, while all other pairs of terminals are neutral relative to each other. based on the OP, I thought I should connect terminal 2 with the door terminal, which I thought was terminal “X” at first because it was located physically very close to the door button, and because the voltage went close to 0 (though actually it was only going from 24 v to ~7v, which should have been a red flag. I guess the reason it was dropping was that there was some leakage across either the talk or listen switches, causing the voltage to drop) when I pushed the door button. However, based on this diagram it appears I actually should have placed the other blue wire on terminal 3. This voltage actuallygoes to 0 when the button is pressed, which makes sense with the diagram as it is a direct connection between the door and power. I will try rewiring the switch and let you know how it goes!

update: It works like a charm! the key is to put the two blue wires on terminals 2 and 3, if you have the door buzzer with the above schematic.

One other note: many wireless hubs, such as wink (the one I have) don’t explicity support this device. However, if you se inclusion/exclusion mode, it will add the device. The important thing to note here is that the hub may not actually turn green when you include the device – mine just continued blinking blue until eventually turning red, which usually indicates a failure for inclusion. However, when I went to my activity history, I noticed a device called “switch” that had been turned on and off. When I clicked the lightbulb icon for the switch it brought me to the products page, where I was able to rename it/add it to a group.

Thanks @lmosenko and @paul

1 Like

I’m not sure if in the circumstance that you guys are using this in matters but in a multiple dwelling situation PK units are generally installed with 1 PK unit. Not one PK unit per dwelling. If you do something wrong you could potentially affect other resident units which could key off management. I wish I could remember how multi dwelling PK units are wired. But I do remember that certain wires are Daisy chained two other control panels. Whenever I worked on them and there was an issue it was usually because a button was sticking in someone’s apartment which in turn affected everyone else’s panel. If you see two separate bundles going in to the panel then you’ll know it’s Daisy Chained. Not saying you guys are going to have an issue, but just something to be aware of.

Interesting reading the solution above - after looking around for a solution for months now, i thought i might share this ( Sucks that it’s not available just yet (hopefully soon).

If anyone has found a solution which is similar that can also detect and send a notification when the door buzzer sound is detected i would love to know about it!

Thanks for that product intro. It is very similar to the z-wave relay we were talking about to earlier. But it is more self contained.

Hi! I will be attempting this solution this coming week. I am purchasing the equipment but I was wondering if a smaller z wave component that I could hide inside the panel would work?

Could I get away with using something like this?
or this:



Did you make any headway with this? Wondering the same thing and would like to change over my intercom.