This high quality circuit with complementary symmetry was found in an Electronics World of 1966. It can be made with modern transistors like the BD or TIP series.
This circuit was published in a 1977 Radio Shack catalog. The PNP transistor may be BD135 and NPN...
Texas Instruments Standard Operational Amplifiers Texas Instruments makes available through Mouser...
This circuit produces an intermittent ring tone being triggered directly by the telephone line. However,...