Advantech PCI-1727U, User Manual

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25 Chapter 3
3. Floating load with the internal 12 V supply
Digital Signal Connections
The PCI-1727U has 16 digital input and 16 digital output channels. The
digital I/O levels are TTL compatible. To transmit or receive digital sig-
nals to and from other TTL devices, the connection should be as follows.
When the PCI-1727U is used to detect an OPEN/SHORT signal from a
switch or relay, a pull-up resistor must be added to ensure the input is tied
to a high ( + 5 V) when the contact is open. The following diagram shows
this configuration.