This read-write enumerated value enables(2) or disables(1) DTMF digit packet transport, where enabling it means dialled-digit packets are only used when the voice encoding scheme cannot transparently pass DTMF tones, and disabling it means a higher-rate encoding should be used instead to pass tones transparently. It matters to an admin troubleshooting touch-tone menu systems that seem unresponsive over a compressed voice link. Setting this to enabled(2) on a low-bitrate encoded line ensures touch-tone digits reach an IVR system correctly even though the codec itself cannot pass DTMF tones cleanly.