Panasonic KX-TDA0484 Programming Manual

Also see for KX-TDA0484: Getting started Programming guide

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Panasonic KX-TDA0484 Programming Manual Manual pdf 23 page image

2.2 ProgrammingProgramming Guide 23Required Bandwidth for Voice Communication via WAN (PPP: Point-to-Point Protocol)When assessing your bandwidth requirements, keep in mind that the longer the packet sendinginterval, the smaller the amount of required bandwidth, and vice versa.However, also consider that the shorter the packet sending interval, the clearer the expected speechquality, because delays in packet transmissions will be small. When the packet sending interval islong, delays are more likely to occur, resulting in overall degradation in speech quality with morepauses and loss in voice communications.Therefore, it is recommended that you select the shortest packet sending interval that networkbandwidth can accommodate.DTMF DetectionA VoIP network does not guarantee accurate end-to-end transmission of DTMF signals because theDTMF signals are coded/decoded during VoIP communications, in the same way as voice signals. Inaddition, packets can get lost during transmission.To compensate for this problem, it is possible to enable DTMF detection for the VoIP Gateway Cardto carry out accurate end-to-end DTMF relay over the network. Upon detecting DTMF signals fromthe PBX, the card encodes the signals and then sends them to the destination, instead of as voicesignals. Then at the destination, the card regenerates the DTMF signals from the received encodedsignals, and then sends them to the PBX.Note that when this feature is enabled, the sending of packets is delayed by approximately 30 ms.Therefore, it is recommended that you disable this feature unless DTMF detection is necessary.FAX Signal DetectionWhen sending fax signals using a CODEC other than G.711, the signals cannot be receivedaccurately at the destination because they are coded/decoded over the VoIP network, in the sameway as voice signals.To compensate for this problem, it is possible to enable fax detection for the card. Upon detecting faxsignals (CED tones) from the PBX, the card automatically switches the CODEC to G.711 tocommunicate with the card at the destination. With the G.711 CODEC, it is possible to assure error-free fax communications to a certain extent.To further assure fax communications, it is strongly recommended that the communicating faxmachines be equipped with the ECM (Error Correction Model) feature, an automatic error correctionfeature. When, for example, the receiving fax machine detects errors in transmission, it can have thesending fax machine resend the relevant data.When using the fax detection feature, the communicating cards must share the same value (either"G.711Mu" or "G.711A") for the parameter Voice CODEC Priority (see "Voice CODEC Settings" in"2.2.2 H.323 Parameters").CODEC Packet Sending Interval20 ms 30 ms 40 ms 60 ms 90 msG.711 84 kbps 77.3 kbps 74 kbps — —G.729A 28 kbps 21 kbps 18 kbps — —G.723.1 5.3 kbps — 18.7 kbps — 12 kbps 9.8 kbpsG.723.1 6.3 kbps — 19.7 kbps — 13.1 kbps 10.8 kbps