This Opto 22 safety cover for solid state relays reduces the chance of accidental contact with relay terminals, while providing access holes for test instrumentation. It is made of plastic for protection against conductivity and clips on for simple attachment to the solid state relay. This safety cover is suitable for use with Opto 22 Power series solid state relays.

Relay switches (also called an electrical relay or an electrical relay switch) use a small amount of power to control a larger source of power connected to electrical devices such as car motors, computers, and lighting installations. A basic relay switch has a control circuit with an electromagnetic coil and a load circuit with contacts and a lever. When current flows into the relay switch, it moves through the coil and a magnetic field is created, which causes the lever in the load circuit to move between contacts, either turning the device on or off. In a normally open (NO) relay switch, when power is supplied to the relay, the load circuit is closed and the power source connected to the relay is turned on. In a normally closed (NC) relay switch, when power is supplied to the relay, the load circuit is open and the power source connected to the relay is turned off. In other types of relay switches, non-moving parts such as transistors or semiconductors can be used as the control circuit to operate the switching mechanism. Relay switches can be controlled with an external switch, such as a light switch, or they can be connected to an automatically switched power source, such as a car ignition. One relay can operate multiple switches, and multiple relays can be operated with a single switch, with each relay operating independently from the other relays in the system.

Opto 22 manufactures controllers for automating equipment, input/output (I/O) systems, solid-state relays, and software products that link electric, mechanical, and electronic devices to networks and computers. The company, founded in 1974, is headquartered in Temecula, CA.