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.

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!



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    11 Discussions


    9 months 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 9 months 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 9 months 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.


    11 months 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 10 months ago

    I have no experiences with databases yet.


    1 year 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
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    Reply 1 year 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.