Direct Connect Modem Pak
The Direct Connect Modem Pak provided a 300-baud modem in a Pak cartridge. It was released in 1985, and quickly became outdated as faster modems came on the market. The included ROM was based on the same software base as the Deluxe RS232 Pak and the earlier Videotex software, but had some nice additions such as true lowercase support.
Much like the Deluxe RS232 Pak, it was based on the 6551 ACAI chip, only with a base IO address of $FF6C instead of $FF68. By modifying the address line circuitry and adding an RS232 socket with the appropriate voltage converters, it was possible to modify the Direct Connect Modem Pak into a RS232 Pak, as described at DCModem to RS232 Pak.
See the Direct Connect Modem Pak manual in the archive.