Preserving the quality of touchtone signals

NMS Communications has developed an innovative technique for transmission of dual tone multi-frequency (DTMF) signals in voice over IP (VoIP) applications.

NMS Communications has developed an innovative technique for transmission of dual tone multi-frequency (DTMF) signals, commonly referred to as touchtone signals, in voice over IP (VoIP) applications.

The technique complies with the two major standards, International Telecommunication Union (ITU) H.245 and Internet Engineering Task Force (IETF) RFC 2833, which address the way in which touchtone signals are carried over IP networks.

For its efforts, the company has been awarded a US Patent. The patent, entitled ‘DTMF tone detection and suppression with application to computer telephony over packet switched networks,’ describes a method to overcome a limitation of IP networks that results in incorrect processing of touchtone signals, due to packet loss or signal distortion.

When these conditions occur, the receiving applications and equipment may not recognise the tones and are therefore unable to deliver the desired response. Such breakdowns can lead to mistakes in application processing.

For instance, interactive voice response (IVR) systems use tones to transmit customer keyed-in responses (e.g., ‘press 1 now to reach account service’), and may not be able to process customer transactions when tones are not transmitted correctly.

The NMS technique provides a method of preserving the quality of the touchtone signals as they travel across IP networks, addressing a general industry concern with regard to quality of service for IP telephony applications.

The first NMS products for which this technique is implemented are the company’s own VoIP media gateway and server platforms.