Two way intercom (CB20505E)

This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991. The integrated circuit is from that period.

OPT3002 Light to Digital Sensor (COM066E)
August 2016 - It can be found at Mouser Electronics the new sensors light to digital OPT3002 from...
MCP9V91 Operational Amplifier
July 2017 - Microchip's new MCP9V91 operational amplifiers with input offset and low drift voltage...
High impedance preamplifier stage (CB4683E)
In the figure we have a high input impedance stage with a general purpose PNP transistor. An NPN transistor...