First, I seriously doubt that it is twenty years old.

Second, it is a digital or analog unit? Usually, the analog units had a charcoal gray enclosure and the digital ones were blue. Regardless, the voice mail unit's ports do not connect in parallel to the lines; they connect to dedicated analog or digital station ports. I'm fairly confident that you have a digital unit.

If you have a digital unit, you will need to determine which digital station ports in the STS were assigned for voice mail port use in flash 65, button 12. Once you determine this, simply connect the two ports of the voice mail unit to these extension ports and your job is done.

Yes, it's really that simple.

PS: Dolphin is just the name that the original developer of this product used. Vodavi marketed under the Dispatch or Talkpath brand names, but they were functionally identical.

Ed Vaughn, MBSWWYPBX