This circuit uses a diode as a radiation sensor. The operational ones are old because the publication is from the 80's, but modern low voltage equivalents can be tested.
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
This audio amplifier circuit is from Ibrape's technical documentation from the 70's. The BC177 can be...
This progressive circuit has a lock allowing coded activation. We found this configuration in...