This biestable circuit was found in a Popular Electronics from the 90s. The circuit has an unusual configuration today, using components of the time.
September 2016 - It can be obtained from Mouser Electronics the new integrated circuit µCC21520...
This circuit is a from publication 1980, but still can be mounted with BC548 transistors for Q1...
This circuit provides a signal when dialing occurs. The circuit is powered by the telephone line...