Found in a September 1992 Radio Electronics magazine article, this circuit generates a pulse as shown in the graph below the diagram. The timings can be changed by swapping C3 and C7.
This circuit can use a pendulum sensor. We found this configuration in a 1994 publication. The...
This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are...
This circuit works both as a preamplifier and activates a relay when speaking in front of the...