This circuit was found in a 90s Wels' Think Tank. The frequency depends on C2 and R3. The handset or speaker must be at least 80-ohm. Observe the low supply voltage.
This is the traditional application of the RCA CA1310 integrated circuit, obtained in a 1972...
This relay circuit with a dual channel MOSFET (not very common today) was found in an old American...
We present a DC-DC converter circuit that can operate with input voltages from 2.4 V to 14 V and...