A very simple but highly efficient combination lock circuit is shown in the figure. Any type of on/off switches can be used, varying from commercially available inexpensive types to more sophisticated ...

This simple combination lock accommodates codes from 1-9 digits long, with the only restriction being that the same digit cannot be used twice. The circuit shows strapping for a 4-digit code, in this ...

When I think of economizer circuits for solenoids and relays, I’m reminded of the phrase, “you can’t have your cake and eat it, too.” This phrase comes to mind because if you use a solenoid economizer ...