The failover scenario grants the smooth and reliable operation of two PBXs side by side, where the second one will be switched to active only after the failure of the first one in order to reduce downtime to a minimum (see figure). This scenario is not only interesting in failure situations, it could also be used in cases of maintenance, repair or upgrade of your telecommunications equipment.
The bypass scenario is interesting for customers who want to keep their old telephone system and add new functionlalities by adding a new PBX in front of the old one (eg by an Asterisk system). With the bypass szenario you have the opportunity to add a new PBX between the PSTN Lines and the outgoing Lines of the old PBX system. In the case of a failover, the PSTN Lines will transparently reconnected to the existing old PBX (see figure).