DTMF Decoders

DTMF (Dual Tone Multi-Frequency) decoders are devices that receive data transmissions in amateur radio frequency bands. They constantly monitor incoming signals for valid DTMF digits. These electronic circuits decode DTMF dial tones from telephone lines into touch-tone phones via a process known as tone dialing. 

The basic DTMF decoder identifies tones from a normal touch-tone phone. It then activates an LED to provide a 4-bit binary signal as an output code.


DTMF decoders are tolerant of level variations, but function optimally at a 0dB range.

What are DTMF decoders used for?

DTMF decoders increase connectivity in electronics to allow better control of applications. Home applications like alarm systems, electronic gates and garage doors, intercom systems and everyday appliances make use of DTMF functionalities. 

Public switched telephone networks (PSTN) and voice response systems are other examples where DTMF application is necessary. 

Types of DTMF decoders

The most common types of DTMF Decoders include 2-tone, 5-tone, multi-tone and burst-tone versions. Multi-tone decoders receive and translate multiple tones from the source, and burst-tone versions decode clashing frequencies into binary signals 

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Description Price Operating Frequency Fabrication Technology Typical Supply Current Minimum CMRR Mounting Type Package Type Pin Count Dimensions Height Length Maximum Operating Supply Voltage Maximum Operating Temperature Minimum Operating Supply Voltage Minimum Operating Temperature
RS Stock No. 313-8091
Mfr. Part No.NJM2211D
- - - - Through Hole PDIP 14 19 x 6.4 x 3.4mm 3.4mm 19mm - +85 °C - -40 °C
RS Stock No. 173-2495
Mfr. Part No.NJM2211D
Each (In a Tube of 50)
- - - - Through Hole PDIP 14 19 x 6.4 x 3.4mm 3.4mm 19mm - +85 °C - -40 °C