Above 2400 hardware flow control must or should be used. This in turn requires full 9-pin cabling out of the RS 232 port, and the external modem must be configured for hardware flow control -- which it would be, one hopes, for a properly-
engineered modem designed for operation at speeds > 2400.
A second requirement is that the terminal emulator driving the cabling and
external modem must be configured for hardware flow control. I'm not sure
what that means in practice, but buzz words are "UART chip" and "RTS/CTS
hand shaking".
Also, it's not clear whether it matters for the Zoomer which may not be
capable of running above 2400 in the first place even though the preference
table lists higher speeds.
Comments? ................................ 'Gene Church