http://gd.tuwien.ac.at/hw-related/hw...yboardPC5.html
5 PIN DIN 180° (DIN41524) FEMALE at the computer.
Pin Name Description Technical
1 CLOCK Clock CLK/CTS, Open-collector
2 DATA Data RxD/TxD/RTS, Open-collector
3 n/c Not connected Reset on some very old keyboards.
4 GND Ground
5 VCC +5 VDC