USER'S MANUAL, VERSION 2.0
Copyright © Convergence Systems Limited 2021, All Rights Reserved
112
6.1
General Purpose Input (GPI)
GPI ports contain an optical isolator inside. The input line has a series resistor of 1K Ohm
with 1.5 Watt rating for protection. This will withstand external voltage up to 36 volt as
shown below.
P = V
2
/ R
P = 36
2
/ 1000 = 1.296 Watt < 1.5 Watt
Therefore the highest voltage the GPI port of CSL Intelligent Fixed reader can “see” is 36
volts.
If one uses the 12 Volt DC output from the CSL Intelligent Fixed Reader in the input sensing
circuit (examples are in next few pages), then that voltage is well below the limit of 36 Volt.