This circuit appears in several versions in publications of the time and can be modified by changing the capacitors. This one is from Radio Electonics magazine from October 1992.
The circuit shown is from the Texas Instruments optoelectronics manual, applying to low power...
This circuit appears elsewhere in this section, but taken from other sources. This is an English...
With 3 transistors, this sensitive circuit was found in the July 1990 issue of Radio Electronics...