The Vivitar SB-4 is an AC adapter that allows the 283 and 285HV flash units to be powered by 110v household current. This is especially useful for use in the studio. It will also decrease the flash recycling time down from 10.4 seconds to 4.8 seconds.
Note: The flash requires fresh AA batteries to be installed, even when using the AC adapter. However, with the current redesigned version of the 285HV (made after 2006), only alkaline batteries will allow it to be used this way.