The operational amplifier and the sensor used in this National Semiconductor circuit are not common today, but the configuration can be adapted to use current components.
This digital pulse counter offers an LED indication. Its maximum frequency is of the order of 5...
This 1960s Signalite circuit uses two SCRs to achieve full wave control. The trigger elements are...
This circuit was obtained from a Popular Electronics. The component is a UJT. The circuit has an...