When VoIP gateways first started hitting the market back in 98′, the vendors tried to packetize DTMF and quickly learned it did not work well.   For this reason they quickly learned to “regenerate” DTMF at the outbound gateway rather than packetize and truck it across the network.   Moving modem tones is even more challenging and most VoIP solutions discourage attempting to send modem tones over an IP connection.  If you can get it to work at all, the modems will [...]