This timer was found in Japanese documentation from the 1960s. The transistor can be replaced by an equivalent and the relay must be of the sensitive type with voltage according to the power supply.
This circuit was obtained in a 1977 magazine, but it can still be easily assembled, as the...
This intercom for the 27 MHz band was found in a recent English documentation, working with a...
This relay shield circuit for old computers was found in January 1983 Radio Electronics magazine. The...