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DTMF Masking

Facts about DTMF Masking for payment security

DTMF stands for Dual Tone, Multi-Frequency, which is the tone that’s given to each key press of a touchtone telephone keypad. When each key is pressed on your phone, it generates two frequencies. One tone is generated from a high-frequency range of tones and the other from a low-frequency group. This means a voice cannot imitate the tones.

As the alternative to asking your customers to speak their card details over the phone is to ask them to type the numbers into the telephone keypad – creating these DTMF tones. While this may have some security advantages these same tones can be interpreted by agents and converted back to real card data. The tones would also be stored in call recordings and systems and so are vulnerable to fraud.

DTMF Payment

Working with Eckoh

To address this issue of interpreting DTMF tones, Eckoh created CallGuard which changes the sound of the DTMF tones to flat ‘monotones’ as they enter the organisations. The tones made by your customer’s telephone keypad are ‘masked’ and cannot be identified by their sound. Any conversation between a contact centre agent and your customer can continue uninterrupted.

Also, the DTMF tones don’t appear in your call recordings either and the data that is tapped into the phone populates fields on the agent’s screen and appears as asterisks with only the last four digits showing as an identifier.

Contact centre payments


Eckoh is the Licensee of Semafone's (Secured by Semafone) "Signal detection and blocking for voice processing equipment" patent family, including GB2473376, which patent describes a technology for same purpose as that designed and implemented by Eckoh in a portion of its products/services.

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