PC817 is your standard optocoupler. Use this IC to isolate two parts of a circuit. Isolation prevents ground loops and prevents trasmission of unwanted noise.Input LED has a forward voltage of 1.2V and a forward crrent fof 50mA. Please use a current limiting resistor as not to blow out the input LED. requency depends on the pull up resistor you use on the output transistor. For applications higher than 1KHz, consult the datasheet.
2.System appliances, measuring instruments
3.Registers, copiers, automatic vending machines
4.Electric home appliances, such as fan heaters, etc.
5.Medical instruments, physical and chemical equipment
6.Signal transmission between circuits of different potentials and impedances