Yes, he is using his DST Communicator to make and recieve calls!
It's a Working BlueTooth Cell phone!
"Bink" writes on the ebay auction:
Greetings fellow Trekkies, Trekkers and Sci-Fi fans! Hold on to your hats cause up for bids is one Screen Accurate, Very Cool, Loud and Clear, Fully Functioning Star Trek The Original Series Bluetooth Communicator! How many times have you wished you had one of these!You want one? Me too! The last just sold on Ebay for $640!
This Comm will pair with any cell phone that is Bluetooth capable! Once paired you can stick your cell in your pocket then send, receive and make calls using your Comm just like Kirk and the boys! Imagine the response you'll get pulling this bad boy out at the next convention! It is full duplex, meaning that both parties can talk at the same time and it even accepts voice commands!
(and watch his YouTube vid, demonstrating & explaining the technology Here!
Don't miss it, it's chocked FULL of Star Trek ennuendo!)