Mobile Intercom With A6 Module and Arduino




About: I like to combine electronics like Arduino's, ESP8266 etc with 3D designing and 3D printing.

In this instructable I show you how I made a intercom using a GSM module.

If you press the big button, the programmed number is called. The call is ended after a programmed time, or by pressing the hangup button.

Components I used:


Arduino pro mini:

A6 module:



Tactile switch, any, like:

Edit: see my other instructable for an improved version.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Tweak the A6 Module

The get sound of the phone call, i needed to tweak the connections of the module on the PCB. On the PCB, the EAR_L and EAR_R are connected to the pins, but I needed the REC- and REC+ connections.

So, I cut the wiring on the PCB and made connections directly from the REC- and REC+ connectors of the module to the pins which previously had the EAR connections

Step 2: Program the Arduino Pro Mini

Attached is the program I used, my program was inspired by Saravanan AL:

Pin 6 and 7 are both pulled up to 5V.

If the button connected to pin 7 is pressed, the programmed number is called

If the button connected to pin 6 is pressed, the "ATH" command hangs up.

Edit: the SoftwareSerial is able to send at 115200, but not able to receive well at 115200 BAUD.

Step 3: Connect All to a PCB

Connect all components to a standard PCB (30 x 70 mm).

The Arduino pro mini also gets a switch to the reset (RST, pulled up by 10k to VCC) pin, to reset the Arduino.

Step 4: Design and Print a Box

In 123D design a designed a box for the intercom. See attached STL files.

The files were printed on a Wanhao Duplicator i3 in Wanhao silver PLA. The box was printed with a 0.8 mm nozzle, the top with a 0.6 nozzle.

Step 5: Add All Together

Finally screw all together and glue in the tactile buttons. The speaker is glued to the top of the box.

Connect to a 5V phone charger as power supply and you are finished!

Be the First to Share


    • Made with Math Contest

      Made with Math Contest
    • Multi-Discipline Contest

      Multi-Discipline Contest
    • Robotics Contest

      Robotics Contest

    17 Discussions


    8 months ago

    Hi! I very appreciate for your help with speaker on A6, I lost a day to understand it)) Almost everythere I find bugs in sketch, but you went further and found bug on pcb)

    2 replies

    Reply 8 months ago

    yes! it worked! I hear the own voice + mic.
    the next phase is mp3-module speak in mic input after call answering.


    Reply 8 months ago

    Thanks for your comments. Great results. I am interested in your finding with speaking via a mp3 module.


    8 months ago

    I have a gsm module but unfortunately it doesnt have an output for mic and speakers. I need to integrate mic and speaker too. In my GSM module, but I dont know how to connect these to speakers and microphone. Does anyone have any idea about this? Please share.

    2 replies

    Reply 8 months ago

    Hello, A6 Mini thanks for your publication I already understood it, it is necessary to make the connection to rec +, rec-, and everything worked ok.


    1 year ago

    Very nice project of yours!

    I'm facing a problem with my microphone.. I can't send any voice via A6 module to any other phone, only recieve sound. When I'm testing with AT+AUST commands the mic works but newer when answering a true call. Yes I know AT+SNFS commands to switch between headset and external rec/mic.

    How do you enable your mic or is it not working as a true intercom? I think this is a softewareproblem, what firmare do you got?

    2 replies

    Reply 1 year ago


    I do not especially enable the microphone, I only send very simple commands to the A6 module via a serial connection (ATD "phone number" and ATH). I did encounter some problems in booting the A6 module properly, but then the whole communication between Arduino and A6 did not work.

    I also had some problems with another electret microphone, but now, afterwards, I think that I exchanged the + and - of the microphone.


    Reply 1 year ago

    Thanks for your kind answer.

    I have seen people connecting resistors, capacitators and inductors to the mic. I only have one electret microphone, but it works very fine when making the sound test by using AT+AUST=(0 or 1). Crisp and clear sound I got when testing, but when answering a call or calling with A6 module only its speaker works. I do not get this. It might be something wrong with microphone but why is it then working when making a6 own sound test.. what am I missing?

    Did you succeed in having a fully functioning (bidirectional) call with your dad and mobile intercom?

    You could switch on and off power supply to A6 module by using arduino instead.

    I would use a resistor to protect A6 and PWR when booting when using 5V.


    1 year ago

    Hello, id like to ask do you have idea how to send Text message received by GSM module to database? Thanks.

    1 reply

    Reply 1 year ago

    I have no experiences with databases yet.


    2 years ago

    Nice tutorial. I have an issue with my A6 MODEM. It shows creg:3 when it boots, but i can not communicate with it. if i dial the line, it shows RING on the terminal, but when I send AT commands, there is no response. What could be the cause? please help, as it is for my final year project. Thanks.

    1 reply
    Wim3dDIY Hacks and How Tos

    Reply 2 years ago

    Thanks. I made this one for my brother to use with his fruit vending machine, for a customer who needs help or needs some change.