Suitable for operation with high impedance microphones, this circuit was found in American documentation from the 90s. The transistor can be any general-purpose type.
We found this circuit in a technical documentation from the 70s. It can be implemented with more...
We found this shield circuit in a 1991 technical documentation. The phototransistor can be...
This circuit was obtained from a Radio Electronics from October 1963. The 4 transistors must be...