Microammeter (T465E)

Found in a 1948 MIT documentation, this circuit uses a 0 to 100 uA microammeter as an indicator. The power supply is 150 V.

Commercial Radio TN603 (CB18406E)
This sixty Japanese commercial radio used 6 transistors in a superheterodyne configuration for...
Intercom Using Electret (CB16273E)
Here is a high-quality intercom for demanding readers. The circuit is from a 1982 documentation. Of course,...
Control Matrix (CB11284E)
This circuit allows to activate three functions in a controlled way, determined by a diode array....