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Can someone explain to me in plain English what SIP trunking is, please? I've read about it on Google, but I don't really grasp it yet. Does it allow a VoIP call to be placed outside of the LAN? So if you had Asterisk setup as the PBX, then IP calls could be made outside of the network? Am I close or am I just saying stupid words?

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migrated from Apr 2 '10 at 6:30

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SIP trunking is connecting the PBX to the regular public telephone network using an Internet connection. It means you can connect an organisational telephone system to the outside world without needing to run voice communications lines, only requiring an Internet connection.

It allows you to make/receive telephone calls from within your phone system to/from the rest of the world, just as if your phone system was connected directly to the regular telephone network.

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You also need to be aware that "SIP" on it's own can & will be used for Telephone Handsets that connect to an old telephone system that can then push the call out via analogue. (wired telephone lines or ISDN - digital lines)

SIP Trunking can as rightly stated be from a telephone system or it could just be a single phone physical or virtual softphone using a SIP trunk to make outside calls (slight over-kill), but certainly possible.

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