The Volex TTX2000 S Issue 1.2 ROM
The Volex Issue 1.2 ROM is a later version of the firmware.
It uses the same teletext acquisition code, but new telesoftware downloader routines written by Martin McBride of Scicon under contract.
The code is common between versions up to $1532 where new telesoftware routines overwrite the previous code. The routine at $1F8D is also used by both ROMs.
Redundant code and data from an earlier ROM remains, but is unreachable and unused. Some of the unused code in the newer ROM differs slightly, suggesting that it was based off a version other than 2.3.
The 4Data telesoftware adaptor ROM Issue 1.2
The 4Data Issue 1.2 ROM is identical to the Volex ROM apart from the data defining the menu screen.