This low frequency oscillator circuit was found in an Electronic Design from the 90s. The transistors are common types, and the frequency is given by the crystal.
With the values of the components indicated, this timer controls intervals from a few seconds to a...
This 80's circuit uses a light-sensitive SCR or LASCR and a one-sided silicon switch SUS, uncommon...
This circuit, found in ancient US documentation, allows you to switch the antenna from the...