This is an older internal dial-up modem card for the Tandy 1000 EX and HX desktop computers. It transmits and receives data at 2,400 bps, a.k.a. 2.4 kbps. There are two built-in telephone jacks.

It connects to the PLUS expansion slot inside the computer, which can be accessed by removing a plastic cover on the system's housing. It may be used to automatically dial telephone numbers.

The Modem-Master 1000 is Hayes-compatible. It was listed in PC Enterprises' 1994 catalog for $89 U.S. dollars. The same company developed many products to drastically upgrade the HX and EX.