This circuit has a visual indication of activation and is suitable for people with hearing impairments. The circuit was found in the March 1974 issue of Radio Electronics magazine.
This circuit works only with carbon microphones, due its low impedance. The speaker should be good or...
The LEDs, in addition to flashing if the transistor is good, also indicate the polarity of the...
This inverter bistable buffer circuit was obtained in a Hands On of the 90's. Next to the circuit we...