This General Electric circuit, in a documentation from the 1960s, allows the use of high resistance resistive sensors with unijunction transistors in a relaxation oscillator.
This 3-component circuit uses an analog indicator. We found it in an old publication....
Pulses in sequence can be generated from a clock input using the circuit shown bellow. Outputs A,...
This circuit simulates a low-level siren and can be supplied with voltages from 5 to 15 V....