Running LED
Two button control
Relay clock
Toggle on-off
Electronic key
Bistable relay

Elevator control
Traffic light

Relay clock

Even if relay logic is now an old technology, I haven't abandoned it. This circuit features 4 stages only, but the schematic is repetitive, so it may be extended. The relays K and K1 work in astable condition and are supposed to send the clock signal to the others.
Once the circuit is supplied the cycle has to be triggered by pressing the button, then it continues without stopping. In order to prevent current back-flows I had to use the diodes. The 1N4007 works fine, but the 1N4148 may work better. The circuit has been tested with a pause of one second. With a shorter time the relays K and K1 may be stressed.

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