The FT-452-G contains an infrared emitting diode, optically coupled to a high voltage darlington phototransistor. It is packaged in a 4-pin small outline SMD package.
The FT-815 series of devices each consist of an infrared emitting diodes, optically coupled to a photo Darlington detector. They are packaged in a 4-pin DIP package and available in wide-lead spacing and SMD option.