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.
Maxim MAX20333 Adjustable Current Limit Switches Maxim Integrated makes available from Mouser...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...
The deviation of characteristics of this circuit normally referred to the temperature is very low....