Introduction. DTMF (Dual Tone Multi-Frequency) signaling is used for telecommunication signaling over telephone line in the voice frequency band between. Overview. The MT module is a low power device DTMF decoder chip. It is a complete DTMF receiver integrating both the band-split filter and digital. Pin configuration of MT DTMF decoder DTMF Decoder Circuit Unit design Figure 6 is the DTMF decoder unit. The circuit is used to decode the mobile.

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DTMF Decoder – MT8870

November 18, This digital output etmf be read in by a computer, which decoser then act decocer a operator to connect the caller’s telephone line to the designated phone line. Scott C 22 June at On the other hand, the onboard LEDs D1 to D4 will light up depending on the tone received, and will remain lit until the module receives another tone. One more thing, am I able to make a “failsafe” function that closes the relay after 20 seconds if the tone “9” was missed?

Logic 1 ‘2’ press and hold TOE: To do that you need to provide a low impedance path to DC signals. I tried unplugging the power and plugging it back in. It seems as if unplugging the phone from the circuit works sometimes. May 02, Scott C 29 October at Do you have an oscilloscope or logic analyzer that you can connect to diagnose what is going on when it’s locking up?


Scott C 19 June at So I tried using less resistance between tip and pin 2. I understand that the 0. I have tried 2 different modules, phones, and cables??

Is it too late to modify my answer? Ok thanks yeah I was wondering in which variable mtt8870 the tone Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket.

Problems with MT DTMF Decoder

At least we learn as we fail. This circuit did not show any response to button presses. Again because when you’re not pushing buttons it decides there are no longer ear phones connected. Yes – you can get it to operate without an Arduino. Basically on the caller side, it is a dial tone generator. Logged asif Beginner Posts: Here is the circuit as it is now, the only difference from the diagram above is the resistor at the top left: To do that, install a 50K – K resistor between the tip and ring lines.

This still did nothing. July 25, I understand most of the circuit. Billy on May 02, Quote After a few seconds of playing with the buttons, the whole thing suddenly stopped responding.

Hi Mark – I don’t know what a sheme is. I must warn you, however that this is a line input and NOT a microphone input.

After some playing around aimlessly, it started working again. I don’t understand the 0. The phone probably senses something is not quite correct and shuts off the driver for protection. DTMF tones are commonly associated with touch-tone phones and other telecommunication systems. Click the image above to enlarge it. I provide a link to the module in the “Parts Required” list above Logic 0 Detection of dial tones is reflected on the bit TOE, while the output Q4, Q3, Q2, Q1 indicate the dial tone that is being detected on the telephony system.


I am not familiar with the dtmf Thank you for providing this. I will try plugging in my computer instead and see if that changes anything, but the sound card on the computer might do the same thing as the phone and stop putting out signal.

So if this tutorial does not help you, then it is unlikely that I will be of any use. I can also be found on Pinterest and Instagram. The lights didn’t all go off, they just stayed in the position they were in and would not react to the keypresses. Once the DTMF module receives a DTMF signal, it will identify the relevant frequecies as described in the table at the beginning of this tutorial, and produce a binary like output.

I only make recommendations of products I have tried.

I tried reducing the resistance again.