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PCI-1718 Series User Manual 34
3.3.3 Digital Signal Connections
The PCI-1718HDU/HGU has 16 digital input and 16 digital output chan-
nels. The digital I/O levels are TTL compatible. The following figure
shows connections to exchange digital signals with other TTL devices:
To receive an OPEN/SHORT signal from a switch or relay, add a pull-up
resistor to ensure that the input is held at a high level when the contacts
are open. See the figure below:
D.GND
DO
DI
D.GND
TTL Devices
+5V
4.7K
D.GND