XD-61 MT8870 DTMF Decoder Module – Phone Tone Decoding Board with LED Indicators & Header Pins

SKU: FA2044-2
Operating Voltage

5V DC (Stable)
Decoding Chip

MT8870 (High-Stability Version)
Input Interface

3.5mm Audio Jack / 2-Pin Header
Output Type

4-bit Binary (TTL Logic)
Indicator LEDs

5 (Q1, Q2, Q3, Q4, and DV Status)
Frequency Range

Standard DTMF Frequencies (697Hz – 1633Hz)
Operating Current

< 10mA (Active Decoding)
Board Dimensions

26.5mm x 24.5mm
Product Description
The XD-61 MT8870 DTMF Decoder Module is a high-precision audio processing board designed to decode Dual-Tone Multi-Frequency (DTMF) signals into digital data. Based on the industry-standard MT8870 monolithic filter/decoder, this module is the go-to solution for interpreting telephone touch-tone signals.
Whether you are building a remote-controlled home automation system via a phone line, a mobile-triggered security gate, or an automated IVR (Interactive Voice Response) prototype, the XD-61 provides a clean, stable interface. It features onboard LED indicators that provide real-time visual confirmation of the decoded digit (0–9, *, #, A, B, C, D). With its standard 2.54mm pin headers, it integrates seamlessly with Arduino, Raspberry Pi, and industrial PLC systems, allowing your hardware to “listen” and react to phone keypad inputs.
Key Features
  • Complete DTMF Interpretation: Decodes all 16 standard DTMF tones (digits 0–9 and symbols *, #, A, B, C, D).
  • Onboard Visual Feedback: Features five LEDs to indicate the binary state of the decoded output and a “Data Valid” (DV) status LED.
  • Integrated Audio Input: Includes a standard 3.5mm audio jack for direct connection to phones, radios, or audio players.
  • Low Power Design: Optimized for low power consumption, making it ideal for battery-operated remote monitoring stations.
  • High Sensitivity: Built-in differential input amplifier and internal band-split filters ensure accurate decoding even with weak signals.
  • Digital Output: Provides a 4-bit binary output (Q1–Q4) that maps directly to the decoded tone, simplifying microcontroller coding.
Usage & Applications
  • Remote Home Automation: Control lights, appliances, or locks by calling a connected mobile phone and pressing keypad digits.
  • Security Systems: Implement DTMF-based gate openers or alarm resets that only authorized callers can trigger.
  • Industrial Telemetry: Remotely query the status of field sensors or trigger machinery resets via radio or landline.
  • Educational Projects: A classic STEM project for teaching signal processing, binary logic, and telecommunications.
  • Automated Response Systems: Build low-cost IVR systems for small business notification or survey tools
Q: Do I need to write complex code to recognize the tones?

No. The module does the “heavy lifting.” It converts the audio tones into a simple 4-bit binary code on the Q1–Q4 pins. Your microcontroller only needs to read these four digital pins to know exactly which button was pressed.

Q: Can I use this with a modern smartphone?

Yes. Simply connect the smartphone’s headphone jack to the module’s 3.5mm input jack. Ensure the phone’s volume is set to approximately 70-80% for the most reliable decoding

Q: What is the "DV" pin used for?

The DV (Data Valid) pin goes HIGH when the module successfully detects and decodes a valid DTMF tone. This acts as an “interrupt” signal for your Arduino, telling it that new data is ready to be read from the Q pins

Q: Can I decode tones from a live phone call?

Yes, provided the audio from the call is fed into the module. This is typically done using an audio splitter or a custom interface that taps into the receiver’s audio line

Q: Is this module compatible with 3.3V systems?

The XD-61 is designed for 5V operation. While it may function at 3.3V, we recommend using a logic level shifter or a 5V power supply to ensure the precision timing required for DTMF decoding is maintained

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