Texas Instruments TI-89 Tip List page 147

The parts list for the original cable:
Designator
D1, D2, D3, D4
Q1, Q2
Q3, Q4
R1, R2, R3, R4
R5, R6
Miscellaneous
The diodes, resistors, transistors, DB-9 connector and are commonly available from many sources,
including Radio Shack, Digikey (www.digikey.com) and Mouser Electronics (www.mouser.com).
Mouser carries a very nice 2.5mm jack (161-3307, $1.47) which I use. As an alternative to this jack,
you could also make a hard-wired pigtail, connected to the BCC printed circuit board, by cutting off one
end of the calculator-to-calculator link cable which comes with the calculator. You can also buy this
cable from TI at their on-line store; look under 'Graphing Calculators'.
The Deluxe BCC
The deluxe BCC is quite similar to the original BCC. A push-pull output stage is added and the resistor
values are changed, so that the circuit draws less current (meaning longer calculator battery life), and
the signal levels at the serial port outputs are increased. The increased level provides better
compatibility with some PC serial ports, which do not really comply with the ±12V RS-232 standard.
Value
1N914
2N4401
2N3906
20kohm, 1/8W, 10%
7.5kohm, 1/8W, 10%
Printed-circuit board (PCB)
Enclosure
2.5mm stereo plug (or jack)
DB9 or DB25 female connector
Hook-up wire
Comments
May also be 1N4148, 1N4004. Not critical.
May also be 2N3904, or any NPN transistor with at
least 25V collector-emitter voltage rating
Any PNP transistor with at least 25V
collector-emitter voltage rating
Any type of resistor will work, also any value from
18K to 24K
Any type of resistor will work, also any value from
5.6K to 9.1K
5 - 5