This low power circuit was obtained from an American 80's documentation. The circuit indicates the voltage of a battery being trimmed by the trigger point. The transistors can be the BC549.
August 2016 - Mouser Electronics is offering the development kit board Joule ™ 570x with expansion from...
In the figure we have a configuration that allows to test NPN transistors and with the addition of a...
This circuit was designed to work with the previous one in triggering a relay by the sounds picked up...