Hello everybody and thank you for your help along these years. I want to share an experience I just had working on my last project. It's an automated gate opener controlled through remote control and/or phone call (DTMF and/or SMS). Everything worked just fine but when I wanted to add an exterior lighting controlled by a LDR I got a weird situation reading the analog input connected to this LDR. The analogRead works perfectly if no SMS has been sent; between 0 and 1023 depending of the light exposure. As soon as the system sends a SMS to confirm gate opening or closing, it "turns crazy" and reads only 1023... After checking on this forum and googling for a while I found that it's only a matter of reference. AFTER sending the SMS, you just need to insert the line analogReference(DEFAULT); Hope it helps.