This circuit was found in Radio Electronics magazine from October 1964. The circuit uses two transistors of the time that require a supply voltage of 9 V. Consumption is 2.5 mA.
The idea of this automation can be extended to other applications that involve the control of...
What differentiates this circuit from the previous one (CB15613E) is the non-need to use a...
Found in Elektor Electronics from the 90s, this circuit produces the tone of 1 750 Hz for calling VHF...