Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This traditional two-tone alarm configuration with the 4011 integrated circuit was found in a 1998...
This extremely slow circuit produces one pulse per month and can be used in a timer. We found it...
This circuit is from an 80's documentation, making use of PUTs that are not currently common...