This very low power amplifier is designed by Amperex for hearing aids. It is based on TAA370 which is not an integrated circuit that can be found today.
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...