© National Instruments Corporation
4-1
ER-8/16 User Manual
Chapter 4
Theory of Operation
This chapter contains a functional overview of the ER-8/16 and explains the operation of each
functional unit making up the ER-8/16.
Functional Overview
The ER-8 has eight SPDT relays controlled by eight digital lines connected to the ER-8. Each of
these relays has an NC contact that is connected to the COM contact when the corresponding
digital output line is low, and an NO contact that is connected to the COM contact when the
digital line is high. The contacts are break-before-make, so all three contacts are never short-
circuited. The block diagram in Figure 4-1 illustrates the key functional components of the
ER-8/16.
