This additional bell circuit was found in the February 1994 Electronics Now magazine. The transistors are common, and the circuit is for analog lines.
This SCS counter circuit was found in a 1964 General Electric documentation. The circuit has a...
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
Operational amplifiers used in this 80's circuit is not very common today, but the setting can be...