This circuit was suggested by Motorola in a 1969 publication. It makes use of components of the time, but both the FET and the bipolar may be general purpose current types.
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...