This circuit was obtained from an Electronics Now from the 90's. It generates the dial signal and the ring tone, serving for testing as well as for demonstrations.
This 1967 Ferranti circuit uses company components. These transistors can be replaced by modern...
This simple thermostat circuit was found in the September 1976 issue of Radio Electronics...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...