Linksys SPA962, SPA942, SPA932, SPA922 manual Dtmf Notes

Setting Regional Parameters

Miscellaneous Parameters

DTMF Notes

DTMF, short for dual tone multi-frequency, is the system used by touch-tone phones. DTMF assigns a specific frequency (consisting of two separate tones) to each key so that it can easily be identified by a microprocessor.

In-Band and Out-of-Band (RFC 2833): SPA9x2 phones can relay DTMF digits as out-of-band events to preserve the fidelity of the digits. This can enhance the reliability of DTMF transmission required by many IVR applications such as dial-up banking and airline iformation.

The following parameters can either help false detection or get better detection by the IVR. In general, the default values are recommended for both IVR functions.

•DTMF Playback Level: Local DTMF playback level in decibels per minute, up to one decimal place. Applicable locally whne a user presses a digit or when the phone receives an out-of-band (OOB) DTMF signal from the network side. Does not affect DTMF transmission. Defaults to -16.

•DTMF Playback Length: Local DTMF playback duration in miliseconds. Affects only OOB. Defaults to .1.

•Inbound DTMF Boost: Controls the amount of amplification applied to DTMF signals. Affects only tones sent by inband method. Choices are 0, 3, 6, 9, 12, 15, and 18 decibels. Defaults to 12 dB.

To help false detection, avoid inband and use OOB. With OOB, the DTMF Playback Length does not matter. If you use inband, use a smaller DTMF Boost value.

To get better detection by the IVR, avoid inband and use OOB. This way, the DTMF tone is reconstructed by the PSTN gateway or the remote endpoint, and the quality is not subject to distortion from the audio codec. If you use OOB, use a slightly longer DTMF Playback Length.

If you use inband, use a higher Inbound DTMF boost.

Linksys SPA9x2 Phone Administration Guide 77