This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is given by capacitor C1 and R2 which has the range of values indicated in the diagram.
We find this circuit in a radio amateur publication of 1977. Its purpose is to measure the...
This inverter amplifier is from a 1992 publication. NPN transistors can be BC548 and PNP BC558....
I found this circuit in a 1986 English magazine. It can still be easily assembled, exchanging Q1...