DTMF Tone Generator & Detector | Free Online Touch Tone Tool

DTMF Tone Generator & Detector

Generate touch tones, dial phone sequences, detect DTMF from audio, and visualize frequencies in real-time. A free telecommunications audio toolkit.

How to Use

Click keypad buttons to generate individual DTMF tones, or enter a phone number to play a dial sequence. Use the Detector tab to decode tones from your microphone or audio files. All tones can be exported as WAV files for use in other applications.

DTMF Keypad

Current Frequencies
Low Tone
— Hz
High Tone
— Hz
50%

Telephone Tones

Sequence Dialer

Tone Duration 150 ms
Gap Between Tones 75 ms
Audio Visualization
📜 Recent Sequences
No recent sequences

DTMF Detector

Input Visualization
Detected Digits
Waiting for input...
Ready

Frequency Analysis

Detected Frequencies
Low Tone
— Hz
High Tone
— Hz
Last Detected Key
—
Detection Sensitivity Medium
Low = fewer false positives, High = more sensitive
Min Tone Duration 40 ms

DTMF Frequency Reference

Each DTMF key generates two simultaneous sinusoidal tones: one from the low frequency group (rows) and one from the high frequency group (columns). This dual-tone design was chosen because it's highly resistant to voice frequency interference.

1209 Hz 1336 Hz 1477 Hz 1633 Hz
697 Hz 1 2 3 A
770 Hz 4 5 6 B
852 Hz 7 8 9 C
941 Hz * 0 # D

DTMF (Dual-Tone Multi-Frequency) signaling is the system used by touch-tone telephones to communicate with the telephone exchange. Developed by Bell System in the 1960s, it replaced the older pulse dialing method. Each button press generates two distinct tones simultaneously, which allows the system to reliably distinguish between actual keypad presses and random voice sounds.

The fourth column (A, B, C, D) was originally designed for the U.S. military's AUTOVON telephone network to indicate call priority:

  • A (Flash Override) - Highest priority, used for critical national security
  • B (Flash) - High priority for urgent military communications
  • C (Immediate) - Important but not emergency
  • D (Priority) - Standard priority call

Today, these keys are still used in amateur radio, some PBX systems, blue boxes (phone phreaking history), and specialized telecommunications equipment.

Standard North American telephone tones:

  • Dial Tone: 350 Hz + 440 Hz, continuous
  • Busy Signal: 480 Hz + 620 Hz, 0.5s on / 0.5s off
  • Ringback Tone: 440 Hz + 480 Hz, 2s on / 4s off
  • Off-Hook Warning: 1400 Hz + 2060 Hz + 2450 Hz + 2600 Hz, 0.1s on / 0.1s off

Note: Telephone tones may vary by country and carrier. The tones in this tool follow the North American standard (defined by Bellcore/Telcordia).

According to ITU-T Q.23 and Bellcore specifications:

  • Tone Duration: Minimum 40ms, typically 50-120ms
  • Inter-digit Gap: Minimum 40ms
  • Frequency Tolerance: ±1.5%
  • Twist (level difference): -8 to +4 dB (high vs low)
  • Signal Level: -6 to -4 dBm per tone