In the figure we have one of the many options found in this section for an intercom using ordinary phones not in use. This was obtained in a Popular Electronics from the 90s.
For trigger high power loads connected to the power grid, nothing better than using a TRIAC. For...
This circuit with 1% regulation aims at replacing mercury cells. We found it in a 1967...
With this circuit it is possible to control a relay up to 100 mA with an extremely low input...