This analog telephone line extension circuit monitors when the line is in use. We found it in the November 1996 Electronics Now magazine.
This circuit was found in a 90s Wels' Think Tank. The frequency depends on C2 and R3. The handset...
We found this circuit in a 1981 publication. We applied an audio signal, for example, a music...
This circuit was suggested by General Electric in 1969 documentation. It provides a maximum output of...