Hardware reference guide

I/O Modules
35013379 02 October 2007 503
Discrete I/O True
High/True Low
Circuit
Descriptions
The following figures illustrate discrete I/O module true high and true low logic
circuits.
Current Sinking describes a physical implementation of the I/O hardware, which
when in the true state, sinks current from the external load.
Current Sourcing describes a physical implementation of the I/O hardware, which
when in the true state, sources current to the external load.
L
O
G
I
C
Power
Supply
Load
Current
Common
Input
Current
Power
Supply
Current Sink Input/Current Source Output
Output
True High/Current Sink Input/Current Source Output
Current
Input
L
O
G
I
C
Load
Common
Current Source Input/Current Sink Output
Power
Supply
Current
Output
True Low/Current Source Input/Current Sink Output
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com