This Opto 22 120D45 solid state relay provides faster response time than an electromechanical relay and resists vibration. The panel mount requires the use of a thermal interface material such as a pad or compound (not included) placed between the back of the relay and the conductive panel or heat sink and is attached with screws (not included). On the front of the relay, four terminal screws attach control and load wires. The diode has an optical isolation of 4,000 VAC, and the device has a voltage rating of 120 VAC and a current rating of 45 amp. It has zero-voltage switching to reduce arcing and to extend the life of the device, with a maximum 1/2 cycle turn on/off time. It also has a built-in snubber for preventing arcing across contacts. This solid state relay is suitable for use in industrial process control applications such as temperature control, motors, lamps, solenoids, valves, and transformers, among others.SpecificationsRelay terminalsScrewCoil typeDCResistance1,000 ohmOptical isolation input to output4,000VInput Voltage120 VACCurrent rating45 ampSignal pick-up voltage3 VDCSignal drop-out voltage1 VDCThermal resistance0.67 C/WOperating temperature-40 to +100 degrees CDimensions*57 x .44.5 x 24.6 mm (H x W x D)Standards metUL (Underwriter's Laboratories)CSA (Canadian Standards Association)CE (European Conformity)*H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back. 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.