What is DTMF?

What is: DTMF?

DTMF stands for dual-tone multi-frequency. It is the telecommunications signalling system most commonly referred to as “touch tone”. It was introduced to the world on 18 November 1963 by Bell Systems in the US.  Older rotary dial / pulse dial phones were quickly replaced as a result. 

The system works by assigning different audio frequencies to the rows and columns of the touch-tone keypad. When you press a key, which corresponds to a number or symbol, the phone generates a tone. This tone combines a high-frequency signal from the column that key is in with a low-frequency signal of the row it’s in. 

DTMF has grown into many applications across telephone networks. Familiar applications include telephone banking, Interactive Voice Response (IVR) functions, or accessing conference services like Zoom, Webex and others.

Business processes depend on DTMF

Things can go wrong with DTMF. It is an audio signal and can lose fidelity as it travels through networks to its destination. Like all modern digital signalling, it can be impacted by jitter and packet-loss.  When it does go wrong, it can be in several ways, including:

  • Digits are not captured at all when the user presses keys at the handset. For example – User presses 9, but nothing is captured.
  • Duplicate digits can be transmitted. For example – User presses ‘2468’, but digits captured are ‘24688’
  • Some digits are not transmitted. For example – User presses ‘2468’, but digits captured are ‘268’
  • Digits are recognized incorrectly. For example, user keys ‘2468’, but digits captured appear like ‘0468’. 

In many of today’s businesses, the telephone is a key customer contact channel. DTMF introduced the ability for customer self-service through simple keypad selection of a menu option.  Ultimately this self-service helps reduce call handling times and call misroutes.

Business processes have developed around touch-tone interactions. Where those interactions are not transmitted and interpreted correctly, those processes fail with cost implications, revenue implications, and customer experience implications.

With the complex dial-plans of international enterprises, many telecoms professionals turn to Spearline to ensure their services are proactively monitored. Spearline’s Voice Assure Platform helps network managers ensure that their inbound toll and toll-free services, or their outbound calling, connect. It also ensures acceptable post-dial delay and functional DTMF transmission. Critically, Spearline helps measure and manage voice channel quality to ensure good conversations.

Find out more about Spearline

Spearline is the telecommunication industry’s leading network intelligence company. We proactively test toll and toll-free numbers for connectivity, audio quality, and more, globally. For further information, or if you have any questions, please get in touch with us.

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