Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 202)

Glossary
Appendix B
BĆ9
instruction is enabled. (It can only be turned off by an unlatch instruction in a
separate rung.)
Latching Relay
A relay constructed so that it maintains a given position by mechanical or
electrical means until released mechanically or electrically.
LED
Acronym for Light-Emitting Diode.
LED Display
An illuminated visual readout composed of lead alphanumeric character
segments.
Limit Switch
A switch which is actuated by some part or motion of a machine or equipment
to alter the electrical circuit associated with it.
Limit Test Instruction
This PC instruction accesses two user-programmed values which are the upper
and lower limits for testing a number accessed by a get byte instruction. This
get byte-limit test combination is a true precondition if the number is between
the upper and lower limits.
Line
1) A component part of a system used to link various sub-systems located
remotely from the processor. 2) The source of power for operation, e.g., 120V
AC line.
Load
1) The power delivered to a machine or apparatus. 2) A device intentionally
placed in a circuit or connected to a machine or apparatus to absorb power and
convert it into the desired useful form. 3) To insert data and memory storage.
Load Resistor
A resistor connected in parallel with a high impedance load so that the output
circuit driving the load can provide a t least the minimum current required for
proper operation.
Logic
A means of solving complex problems through the repeated use of simple
functions which define basic concepts. Three basic logic functions are AND,
OR, and NOT.
Logic Diagram
A drawing which represents the logic functions and/or, not, etc.
Logic Family
Group of digital integrated circuits sharing a basic circuit design with
standardized input-output characteristics.