Definitions for "DBu"
Decibels of audio power where 0dB is referenced to 0.775 volts of audio voltage in any impedance. The preferred usage is dBu.
A unit of measure of an audio signal in an electrical circuit, expressed in decibels referenced to .775 V RMS into any impedance. Commonly used to describe signal levels within a modern audio system. 0dBu=.775V
Decibels referred to the voltage equivalent of 0 dBm into a 600 ohm load. 0 dBu = 0.775V = -2.2 dBV
Diazabicyclo[5.4.0]undec-7-ene, or more commonly DBU, is a chemical compound and belongs to the class of amidine compounds. It is used in chemistry as a catalyst and complexing ligand and non-nucleophilic base.
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 (!@#$ happens, after all) and have a DBU system in place.