Tandy PLUS Serial Board The PLUS Serial Board was used with the Tandy 1000EX and 1000HX. It plugged into the PLUS expansion bus and had a single DB-25 RS-232C connector. It was capable of supporting port speeds of only up to 9600 bps reliably since it used the earlier 8250 UART chip. The most common use for this board was for adding an external modem which was faster than the Tandy 300 bps and 1200 bps modems available internally for these machines. It could also be used to add a serial mouse to the machine for use with such programs as 'Deluxe Paint II' from Electronic Arts, though this usually required the use of an adapter to plug the DB-9 connector of the mouse to the DB-25 connector of the serial port.

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