Transistor microammeter (CB22302E)

This 10 mA microammeter circuit can measure currents of 50 uA. The circuit is from a publication from the 60's. The transistor is germanium.

Signal Follower LM380 (CB13326E)
Both the field effect transistor and the integrated circuit of this 1970s circuit are no longer very...
Timer with Relay 14538B (CB18466E)
This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is...
Alarm Siren (CB19985E)
The transistors in this circuit, found in an American publication in 1975, can be replaced by...