Interlink VOIDAX! It’s the Interlink 14.4K modem listed in the main post.
Listed on eBay…
https://ebay.us/m/pvdT4M
This is the modem I had and when you powered it on it played an ear splittingly loud Australian male voice saying, “WELCOME TO VOIDAX!”
My dad bought it from Rod Irving Electronics in 1988 from memory. Was love at first sight for me and I’m still in the telco/broadband industry.