The board was designed around an 6850 ACIA's (IC's D & E). Baud rate
and address selection was selected by jumper wires on the board. Each
ACIA utilized two I/O ports. The board was often used in those early
days with Teletype Corporation's ASR33 "Teletype". Later versions of the
ASR33 had an RS-232 hookup option but earlier machines relied on a 20mA
current loop connection. See
here for some
issues using the latter.
The manual for this board (with code examples in octal!) can be obtained
here.
