Found in Motorola documentation from the 90s, this circuit makes use of a triac from that time. The circuit is for the 110 V mains but can be modified for other grid voltages.
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...