Complex sentence: The second server will immeditaly take over the work of the first server as soon as it detects an alteration in the "heartbeat" of the first machine and some systems have the ability to page or send a message to a pre-assigned technician or center.
Split into simpler sentences: The second server will immeditaly take over the work of the first as soon as it detects an alteration in the "heartbeat" of the first machine. Some systems have the ability to page or send a message to a pre-assigned technician or center.