The setting of the data format for the Serial Port defaults to an 8-bit rather than a 7-bit data format. While many telecommunications systems use 8-bit, most of the popular information systems such as Dow Jones and the Source use 7-bit. Attempts to communicate with 7-bit systems lead to garbled information when the default goes unchanged. A command to the software changes the data format on some terminal packages, but others may not allow this command, rendering them useless.
Of all the modems tested, only the Apple modems don't care about 8- or 7-bit data format settings.