The electronic circuit shown in this circuit diagram, can be used as a remotely momentary actuated button.
When light falls on the six solar cells connected in series, T1 goes into conduction, resulting in blocking of T2 (C2 loading).
When solar cells are not lit, T1 and T2 drive crashes. Capacitor C2 is discharged through the LED electronic relay, which is activated for a moment. In this way we generated a trigger pulse equipment of electrically isolated, no need extra power supply.
In the scheme, C1, R1 and R2 ensure stable switching. The solar cells used in the prototype allowed a effective range 2 to 3 m