How to Test the DTMF Inband for VoIP

Updated April 17, 2017

DTMF stands for "Dual-Tone Multi-Frequency." It is a telecommunication signalling feature used in a VoIP (Voice over Internet Protocol) system. "In-band" signalling is the process of sending metadata and control information within the same band and on the same channel. When you dial a number, it is encoded and transmitted across a telephone line as Dual-Tone Multi-Frequency (DTMF) tones. As an administrator, you can test your DTMF on an Asterisk server using the "Dial" command.

Log in to an Asterisk server using administrative credentials.

Double-click to open a "Command prompt" or "Terminal window" (depending on your system) from the desktop.

Type the following without the quotes:


Press the "Enter" key. Replace "" with your own VoIP number, and replace "" with the VoIP number of your contact. The "W" causes the pause when you enter this command. For example: "Dial(5551112222@3334447777,180,D(w*w1w3))."

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About the Author

Suvro Banerji is a recent graduate of the Missouri School of Journalism where he earned a dual degree in broadcast news and political science. He began writing professionally in 2005 at KOMU-8 News (NBC) where he worked as a multimedia producer. Banerji has also interned with CNN for two consecutive years.