A photocoupler is a component that allows the transfer of signals between two circuits using light radiation as the transmission medium. The two systems are galvanically isolated from each other, both security of the entire system and the operator. Are formed by a sender, which in most cases is a LED and a photodetector that typically identifies phototriac or phototransistor.
The MOC3021 has a triac output and an infrared light emission source of gallium arsenide LED. It is largely used in lamp, motor, solenoid and valve control.
Isolation voltage: 7.5KV
Forward voltage: 1.3 ~ 1.5 VDC
Maximum forward current: 50mA
Trigger current: 15mA (max.)
Output current: 1000mA (max.)
Output voltage: 400V (max.)
Power dissipation: 300mW (max.)
For more info download datasheet.