This circuit is from a 1964 Electronic Design. The transistors are from that time. They can be replaced by current equivalents.
This circuit monitors an old-style analog telephone line. We found it in the September 1991 issue...
This circuit was found on a Radio Electronics of July 1984. It consists of a source with the 741...
This circuit, found in an old magazine of the year 1968, uses a Power germanium transistor. This...