This circuit is from a 1969 Electronics World. The transistors may be modern general-purpose equivalents. The circuit is for frequency ranges between 250 Hz and 250 kHz.
IDT ZSSC3230 Capacitive Sensor Signal Conditioner Available from Mouser Electronics stock, this IDT...
This circuit uses only two common transistors and provides good audio power in a speaker. Readers who...
This is the analog part of the previous circuit with the pressure sensor for the altimeter. The...