Found in a 1964 General Electric documentation, this circuit uses PUTs that are not currently common components. By changing the capacitors, the frequency can be changed.
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...