Italian to English Tech/Engineering Computers: Hardware circuit board

I'm stumped with this.
The entire text reads:

F1-F2 In indica un’ attivazione della fotocellula quando il prodotto entra nel raggio d’ azione della fotocellula, cioe’ **sul fronte di salita del segnale prodotto FOTO F1/F2.**

So far I have written: F1-F2 In indicates that a photocell is activated when the product enters the radius of action of the photocell, i.e.

F1 and F2 by the way refer to photocell 1 and 2.

Many thanks in advance