What Is Dual-Tone Multi-Frequency (DTMF) Signalling?  

DTMF revolutionized telecommunications signaling as we know it

What is Dual-Tone Multi-Frequency (DTMF) Signalling?
Contact CentreInsights

Published: June 1, 2023

Charlie Mitchell

Dual Tone Multifrequency (DTMF) is a contact center solution that enables and ensures compliance.

Companies often implement it as part of a PCI compliance strategy to handle personal information and transactions over the phone.

The term is one of many acronyms used in customer service. Others include IVR, ACD, and CRM, which all contribute to the unique language of contact centers.

Each acronym refers to specific tools, systems, and methodologies contact centers use to drive better customer and employee experiences.

DTMF is no different, and here is everything companies need to know about the technology. 

What Is DTMF? A Definition

DTMF is a technology that sits inside touch phones. Every key on a telephone keypad generates a specific “tone” or sound when pressed. These tones transmit over a voice channel to particular technology within the contact center. The technology listens to each tone before translating them into specific commands, such as entering a number from a credit card or providing details on a customer’s data of birth.

DTMF tones signal to a phone system that a user wants to complete a particular action, sending frequency-based commands to back-end technology. The tones in DTMF technology are “dual-sided” because each key sends two tones, one in high frequency and the other in low frequency.

How do Contact Centers Use DTMF?

Modern contact centers use DTMF in a multitude of ways. It’s often part of IVR (Interactive Voice Response) systems and can help users to navigate calling menus, transferring them to the right agent.

Using DTMF in an IVR system means a caller simply needs to push a number on their keypad that corresponds with the menu option they want. For instance, an IVR might ask a user to press one to speak to a customer service agent.

Also, organizations sometimes use DTMF as part of transactional interactions. It allows users to “key in” account and order numbers, passing them through to the system without needing a consumer to tell an agent their details.

How Can It Support Security and Compliance Strategies? 

DMTF tones are crucial in helping customers navigate their experience with a contact center. They can help with routing a client and streamlining different interactions. However, their biggest value is related to security and compliance. With DTMF tones, companies can accept credit card payments over the telephone without an agent ever hearing the details of the card number.

In some cases, when a conversation includes payment card details, DTMF “masks” or “suppresses” them to further reduce the chance of an agent hearing sensitive information. 

Also, DMTF tones enable customers to use their telephone keypads to complete transactions securely and ensure companies can comply with PCI standards.

Finally, with DTMF tones, the caller’s details are not accessible to any agent handling the conversation, and they’re not stored within the call recording software either. This makes DTMF masking more secure than alternatives like pausing call recordings when customers share payment information.

What Is the State of DTMF Today?

DTMF is still in use (in varying degrees) across different parts of the world, although there are several alternatives to replace it. When mobile networks first came into being in the 1990s, DTMF support carried over from PSTN lines – but with every new generation of mobile technology, starting with 2G, DTMF support has steadily declined.  

Indeed, there are next-generation telephones that use the data channel of mobile networks to transfer signals and are, therefore, not dependent on DTMF. 

Moreover, analog telephone adapters (ATAs) can now make DTMF-era phones compatible with the new protocol based on data packets and fiber lines.  

Another emerging alternative to DTMF is voice recognition. True voice recognition technology allows smartphones and computing devices to decode human language into a machine-readable format, eliminating the need for an intervening protocol. 

While some companies have had an early start to voice recognition adoption, DTMF is still the default for PSTN lines for its obvious widespread compatibility advantage and low barrier to entry.  



Security and ComplianceTechnology Media and Telecoms

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