The Apple 300/1200 baud modem supports data formats up to 8 bits. There is
no command to change the data handling of the modem from 7 bits to 8 bits.
When data is sent to the modem, as a series of level transitions, the modem
simply converts those transitions to frequency shifts. It does not care what
the data structure is, up to the specified limits, and will echo whatever is
sent to it.