PSTN <-- > Legacy PBX <-- > IVR
An IP PBX such as the MX250 also supports these interfaces which can be used to connect to the IVR system and to the PSTN. You should be able to put the MX250 in place of the legacy PBX as follows:
PSTN <-- > MX250 <-- > IVR
With this configuration, the new call flow will be the same as it was before. If the call center is also planning to update their IVR, it is best that they choose one that supports VoiceXML and the VoIP protocol SIP. One such IVR is that from Vocomo Software.
This was first published in January 2005