This circuit was obtained from a Radio Electronics in February 1965. The circuit uses two transistors from the time and can be created with modern equivalent transistors.
This source was found in Philips' 60s documentation. The transistors are from the era and the...
This circuit is the digital indicator for the previous circuit and can be used with similar...
Found in a 90s Electronic Design, this circuit operates with Maxim components of the time. The...