Videoconferencing gateways provide a method by which IP based systems can communicate with other types of network based systems, primarily ISDN. In general, a videoconferencing gateway provides ISDN PRI/BRI interfaces for direct connection to telecommunications networks. Calls can be made either from the ISDN side, dialling the ISDN number(s) of the gateway, or the IP side, using a prefix followed by the ISDN/Telephone number of the remote system (note: this requires a gatekeeper).

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