The AN2006 provides USB control of 16 photo-transisitors.

Features

Independently optically isolated collector-emitter pairs provide reliable and demonstrable isolation between a host system and target electronics

Limitations

The output is subject to the intrinsic limitations of the particular transistor used in the isolator circuit.

Pinout

Output is provided by a 34 bin .1" spaced connector.  Pin 1 is designated by an arrow molded into the connector housing.  Odd pins are the collector side of an individual transistor.  The even pin directly below it on the connector is the corresponding emitter side.  Pins 33 and 34 are connected to the USB system ground.