Circuit and Working. Circuit diagram of the laser security system using a basic feature phone is shown in Fig. 1. It is built around two light-dependent resistors (LDR1 and LDR2), five transistors (T1 ...

6V laser security system circuit. Here I have wired in a such a way that the password is UP,DOWN,UP,DOWN. Here there are 16 possibilities. If you use centre positioned then there are 64 such ...