National Instruments PC-DIO-24/PnP - Manual (Page 40)

Chapter 4 Theory of Operation
© National Instruments Corporation 4-3 PC-DIO-24/PnP User Manual
Digital I/O Connector
All digital I/O is transmitted through a standard, 50-pin, male
connector. Pin 49 is connected to +5 V through a resettable protection
fuse. You can use this +5 V supply to operate I/O module mounting
racks. Even-numbered pins are connected to ground. See the Optional
Equipment section in Chapter 1, Introduction, as well as Chapter 3,
Signal Connections, for additional information.