This attribute specifies the DTMF regeneration parameter used
during negotiation with the remote end across the subnet.
If dtmfRegeneration is on, it is desired that DTMF tones received
from the link are first converted to digits before being sent to the
subnet. When a digit is received from the subnet, its respective
DTMF tone is desired to be generated before being sent to the link.
If dtmfRegeneration is off, it is desired that DTMF tones are
transported transparently as audio.