This circuit uses a 555 (according to the diagram) to generate 50 ms tone bursts at a frequency of 1.5 kHz. The circuit is from an 80's Electronic Design.
We found this circuit in a 1965 Electronic Design. Transistors are still common but admit...
This very low consumption circuit can be powered by a solar cell. The time indication is given by a...
We found this circuit in a documentation from the 50's. The transistors are germanium types. The...