These are C64 cartridges made by Richvale Telecommunications from Richmond Hill, Ontario, Canada. They provide the C64 with an IEEE interface for connecting the older 4040, 8050 drives etc.
The RTC Link was the original version. Created in 1982, it offered an IEEE connector and BASIC 4 extensions.
Download EPROM firmware here (caution: not verified).
The RTC Link II was the followup version, released in 1984. It offers an IEEE connector, "link" connector and BASIC 4 extensions. The link connector was used for networking multiple machines together.
Manual available here. Download EPROM firmware here.
Last updated: Jun 1/2011, 1:15pm EST
Send comments or feedback to Steve Gray(sjgray@rogers.com)