An electronic timer with alarm that uses very few electronic components can be designed using this electronic scheme. Asynchronous binary counter with 14 stages, 4060 type, has built in an oscillator with good stability in operation, a relatively wide frequency range. In the electronic diagram below oscillator frequency is determined by an external RC network connected to pins 9, 10 and 11.
Using some electronic components can be made a very simple electronic lock. The electronic lock is based on a single active components. The keyboard can be purchased from the store or can be made using "push buttons".
Four buttons are connected in series (those marked with S1 + S4 in the scheme) between plus and the power transistor T1 through a 1k resistor.
The other four buttons (marked with S5 + S8 in the diagram) are connected in parallel with R2, between the T1 and ground. Relay will be activated only if S1-S4 are pressed, while none of the buttons is pressed S5-S8.