Specifically designed for the HVACR industry, definite purpose (DP) contactors are electrically operated switching devices. They are used for switching a power or control circuit, and are typically ...

This chapter covers representative general-purpose relays used in the control circuits of most industrial, commercial, and consumer products. Relay names and terminology are in accordance with ...

Relays and contactors use a variety of technologies to switch signals and power connections. Many devices called relays use similar techniques and topologies, but the terminology can be confusing.

Last month’s column introduced the concept of an interlock. An interlock is a dependency between two processes. Process 2 cannot operate unless Process 1 is in a certain state. For example, if a ...