National Instruments SCB-68 - Manual (Page 69)

Chapter 5 Adding Components for Special Functions
SCB-68 Shielded Connector Block User Manual 5-24 ni.com
Special Considerations for Digital Inputs
If you use the V
in
voltage of Figure 5-20 to feed TTL signals, you must
calculate V
in
so that the voltage drop on R
2
does not exceed 5 V.
Caution A voltage drop exceeding 5 V on R
2
can damage the internal circuitry of the DAQ
device. NI is not liable for any device damage or personal injury resulting from improper
use of the SCB-68 and the DAQ device.