Radio Shack TRS-80 Videotex

Motorola integrated the functions of many smaller chips from the Green Thumb Box into one chip: the MC6883 Synchronous Address Multiplexer (SAM). The SAM, VDG, and 6809 were used as the core of the AgVision terminal. The system was sold through Radio Shack stores as the TRS-80 VideoTex Terminal around 1980.

This diagram was acquired from Jerry Heep along with other Videotex-related documents from his collection. 

I haven't checked back with him regarding the header, "Videotex II"...