Download the TLP621-4 datasheet PDF.
This datasheet also covers the TLP621 variant, as both devices belong to the same transistor optocouplers family and are provided as variant models within a single manufacturer datasheet.
The TLP621, TLP621-2 and TLP621-4 series of optically coupled isolator consist of an infrared light emitting diode and an NPN silicon photo transistor in a space efficient Dual In Line Plastic Package.