Build Log: TOS Intercom Wall Unit


Introduction: Let’s Make an Intercom!

I’m embarking on a project to create another TOS intercom unit, and I had some requests to do a build log. So I created this post to introduce the project and get started. I hope someone will benefit from it. Please, if anyone has any feedback or suggestions for doing something better, as the Ferengi say, “I’m all ears.”

So what do I want to accomplish with this build? My goals are:

  1. To have the intercom built into a box which represents a section of Enterprise corridor wall. The unit can be hung on the wall or sat on a table top or shelf. This will require care in planning where the power adapter will plug into the unit. I prefer to use a “wall wart” DC power supply because I detest having to change batteries, although having a wired connection to the prop can be cumbersome as well.

  2. Function like the screen used prop.

  • Obviously I want the white oval next to the speaker to toggle from the white Captain’s chair type button. That’s a given.
  • The “big red button” should toggle the flashing alert beacon.
  1. Some extra “bells and whistles”
  • A momentary switch on the side of the unit can be pressed to play the intercom whistle sound effect.
  • You can toggle the alert mode from another momentary switch on the side of the unit. By default the flashing will be fast and silent. The other mode will be a slower flash with the red alert sound effect.
  • Another momentary switch on the side of the unit to activate continuous audio mode. I have a library of intercom dialog MP3 files I have recorded from various episodes. I edited each one to be preceded by the intercom whistle. When this mode is active, every 5 or 10 seconds (I haven’t decided at this point) one of the intercom dialog files will play. They will be played in order, starting from the beginning when the end of the list is reached. Also, when this mode is active, no other sound effects will play.
  • A volume up/down switch.

The electronics will be built using an Arduino Mega and an MP3 player shield available from Adafruit. The faceplate for the intercom will be laser cut acrylic from MDF wood will be used to construct the box, aka Enterprise corridor section. Other parts and my sources for them will be in the next post.

Please join me in this journey and let’s have some TOS prop fun!


I love reading through these build logs. I see you hate batteries, but perhaps some interchangeable lithium batteries? (Or one of those large USB Powerbanks). Have one on charge whilst the other is in use? I guess it depends on the power usage.

I look forward to seeing how you get on :+1:


Thanks for the suggestion. I’ll look into that. I’m also thinking about looking into a USB rechargeable power supply.


Thanks for starting a thread with this, it appears several of us are interested and a few of us even have started a TOS Wall Intercom build ourselves. Arduino is new to me but very interested to learn. This has great potential as a perfect beginner Arduino project to start learning the basic of the platform with your guidance and expertise of having already done one of these and a couple TOS Blinky Lights and Sounds Computers.

You mention this is a second Wall Intercom build, any plans to make both function as a household intercom between the two units?

Will be following with great interest as I’m in process of scratch building a Wall Intercom myself which has been a back burner project that I work on a little here and there. Panel is cut from 1/4” MDF

Grabbing :popcorn: and settling in for this thread!


The first one I built I wasn’t 100% happy with. The box housing has visible seems, and I didn’t do a good job attaching the red alert beacon and intercom speaker. Plus I have learned so much more about electronics, so I can do a better job with that. This will not be a functioning intercom system.


This sounds interesting, looking forward to more.


I am also building a Wall Comm.
Looking forward to see what you do with this one.


So let’s talk about dimensions. Is there an accurate measure of any of the screen-used pieces out there on the webz (or perhaps NOT on the web?), or have people just been guesstimating all these years?

Is there an agreed upon set of plans that someone would consider accurate?

There’s some Arduino code here, not sure if it’s worthwhile.

Interesting threads here and here.


Great question Joel, for me this has been a back burner project so it has been a while but I think I got dimensions from this TFW thread. Even posted a photo in it of a foam core mock up that I had cut back then as an early stage to get a feel of the size and scale.


Here are the measurements I’ve been going by. Thanks to our friends at


^ I believe those are in the TFW “CAD Models” thread linked above.

Will Smith @tosgraphics is a member here, hope he’ll help contribute in this thread.


Those dimensions were scaled from the red button which I have many originals (not screen-used, just the same that were used in the series) and are a known dimension. Pretty much everything was scaled from that using some pretty good screen-caps and basically up-scaling the entire unit to match the button. The above dimensions may be slightly off but they are very, close. We built 5 or 6 of these for STC which were self contained, fully functional and would just hang on any wall section by two screws which fit into holes in the back. Looking forward to your progress.

Here are the dimensions of the intercom unit that I made for the helm console restoration a few years ago. The corner radius of the speaker cutout is 1/2".


Thanks, Will. The info is greatly appreciated.


Thanks so much. Great information.


Step 1: Gathering the Parts

Let’s take a look at the parts I have assembled for this build and my sources. I think this covers the major components needed. If I omitted anything, I will edit this post to include the missing items so this parts list is comprehensive.

Arduino Mega Microcontroller: The Mega is the backbone for the electronics of this build. The code I write will be uploaded to the Mega and will respond to switches, play sound effects, and turn on/off LED’s at the appropriate times. I’ll cover the wiring and program code in a future post. You can pick up an Arduino Mega from just about anywhere from Amazon to eBay.

Adafruit “Music Maker” MP3 Shield for Arduino w/3W Stereo Amp - v1.0: This Arduino shield plugs directly into the Mega and will play MP3 files on command via program code. This shield has a built-in SD card reader, so the MP3 files for the intercom sound effects will be saved on an SD card and placed in the shield’s SD card reader. The shield also has outputs to attach speakers. This is available for purchase at Adafruit.

3” 8 ohm 1 Watt Speakers x2: Speakers to attach to the MP3 shield to output the sound. I usually pick these up from eBay.

5v 8amp Power Supply: This is a typical “wall wart” DC power supply available from Amazon or eBay. It needs to have a 2.1mm barrel output jack so it will fit into the next part.

Panel Mount 2.1mm DC Barrel Jack: The power supply will plug into this barrel jack mounted to the prop and power the electronics. Available from Adafruit.

On/Off Switch: You can pick up some on/off switches from just about anywhere. The one I am using has an LED which indicates when the switch is on.

Momentary Switches x 3: We need these switches to play the whistle sound effect, to toggle alert mode, and to toggle continuous audio mode.

Volume Up/Down Switch: This is a rocker momentary switch and will adjust the volume of the sound effects.

Soldering Iron and Solder: Yes, soldering is required for this project. It’s a terrific skill to have, so if you don’t know how to solder, there are many resources available on the internet for learning this valuable skill.

22 Gauge Wire of Different Colors: 22 gauge is the best option for wiring up components to an Arduino. Also allows you to create your own jumpers for easy connect/disconnects.

Dupont Jumper Kit and Crimping Tool: This kit comes with male/female header pins and housings to create your own jumpers/connectors. A special crimping tool is required to attach the header pins to wire. Using the crimping tool to create these connectors is tricky and takes some time and practice. Both the kits and crimping tools are available on eBay.

Breadboard with Jumper Wires: A breadboard is used to prototype a circuit. You can pick up a breadboard with jumper wires from Amazon or eBay.

Adafruit Perma-Proto Quarter-Sized Breadboard: We’ll have to make our own board to marry up the Arduino Mega with the switches and LED’s. This breadboard available from Adafruit allows us to quickly make our own board by soldering components just as they are on our prototyping breadboard.

Other electronic components, such as resistors and transistors. I’ll cover the specifics of those components while I prototype the circuit in a future post.

White Comm Button (or Captain’s Chair button): Functioning replicas of these buttons are available from Trek Props and Stuff.

“The Big Red Button”: These are usually available on eBay. Search for “Honeywell 12MA6”.

Micro Switch for “The Big Red Button”: The button itself is not a functioning switch. This component attaches to the button and makes it into a functioning switch. These are usually available on eBay. Search for “Honeywell BZ-2R-P1”.

Alert Beacon with Red Lighting Gel: Also available from Trek Props and Stuff.

.005” Sheet Styrene (White): This is paper thin sheet styrene which when placed behind the red lighting gel for the alert beacon will diffuse the LED’s and eliminate any hot spots.

5V LED Strips: We’ll use LED strips to illuminate the alert beacon. A strip can illuminate the oval on the intercom speaker as well.

Intercom Speaker and Speaker Clothe: There are a few different sources for these. Trek Props and Stuff and an eBay seller named jonia_c usually have these available.

Intercom Faceplate: The faceplate will be laser cut acrylic from In a future post, I will talk about the Adobe Illustrator file I upload to Ponoko to guide the laser cutting process.

In my next post, we’ll get the MP3 shield ready to prototype the circuit.



Honeywell MA’s have always been a pricy get but that’s the only thing to use if you want the accuracy.

Others have used arcade type large button switches which will pass if you don’t care about accuracy.


Yes, the authentic Honeywell 12MA6 buttons are quite pricey. Trek Props and Stuff has a nice looking, affordable alternative.


Those replacement red buttons you linked too look like pinball machine flappers and are not anywhere close to the originals. The red button part is too small and the outer bezel is too big and completely the wrong shape. Accuracy has a price and I know I would not be happy using anything but the correct parts. The other white push-button switches actually were made by Mike Paugh (who is a member here) and were based on direct measurements taken from the original captains chair control panel owned by Dave Arland (also a member here). You can not get any closer to an original Hetherington switch than these. Here is a photo of the correct red button with one of MIke’s replicas:


I agree the arcade button leaves much to be desired, but it is presented here for those looking for a low cost alternative. For this build I am using the genuine Honeywell button and micro switch.


Ahhh, got it!