Dial back up. Basically, if the main circuit goes down, the remote router will connect to the host via means of a 56k modem or ISDN circuit. This is a fairly inexpensive means of ensuring that your business is not impacted when a circuit outage occurs. (It won't help you if the local phone lines go down due to a cable cut or accident knocking down poles, but if it's a circuit issue beyond the local CO, you'll probably be able to use the phone line successfully as a backup.)I've never understood why so many customers don't plan ahead for outages (
[email protected]#$ happens, after all) and have a DBU system in place.