With an 18 V input, this regulator was found in Philips documentation from the 60's. The transistors are from that time. The power transistor must have a heatsink.
We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio...
This field strength meter circuit was found in the March 1968 Radio Electronics magazine. The...
I found this circuit in a 1998 publication, but as all components are common, it can be easily...