This notch filter was found in National Semiconductor documentation from the 1980s. Operational amplifiers are from that era. The configuration can be adapted to use modern operational amplifiers.
This timer with 1 second accuracy was obtained in a 1973 documentation. The Buzzer is a low-power type...
The sensors in this circuit are NTCs and PTCs that work in a differential way by directly...
The presented circuit is suggested by Texas Instruments (www.ti.com) in its Application Report...