Despite being from a 1969 publication, the transistors used have current equivalents such as BC548 and BC558. The circuit generates signals from 1 500 to 20 000 Hz and 4 scales.
This interesting source of very low voltage for reference finds applications in the...
This sonic switch, sound relay or simply vox uses a medium impedance speaker as a microphone. The...
Using red LEDs with ignition voltages of the order of 1.5 V we can make a multiple voltage...