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 circuit was suggested by National Semiconductor in its Linear Application Handbook. The...
This circuit was obtained directly in the component's datasheet, and in it we have the use of...
This 3-channel configuration was found in a 1982 Selezione Radio magazine. The publication no...