This circuit was obtained from a 1969 Electronic Design. Transistors admit modern equivalents. The frequency of the signals is set to R2.
This circuit functions as a thermostat triggering a relay when the boil control temperature...
The figure shows how to connect a relay to obtain the latch effect. The circuit is from an...
With this circuit it is possible to use a DC buzzer (not a transducer) as an extension of the...