This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog indicator and the transistor is a general purpose one.
The CMOS TLC555 can be gated from external CMOS circuits using the configuration shown here. The...
In the figure we have a two-channel preamplifier with two 741 integrated circuits. The circuit is from a...
We found this circuit in a documentation from the 50's. The transistors are germanium types. The...