Sensoray 2253 - Manual (Page 11)

Model 2253 has 2 general purpose inputs (GPIs), and one general purpose output (GPO).
One of the GPIs and the GPO are opto-isolated. The second GPI is galvanically coupled.
The opto-isolated GPIO and recommended circuits are shown in Figure 2.
Figure 2: Opto-isolated GPIO.
The GPI-C1 is a galvanically connected GPI. It provides a simple way of communicating
with the 2253 in cases where optical isolation is not required, by means of shorting this
signal to the ground (pin 15 of GPIO connector). Please see the Software Reference for
details.
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