In use telephone indicator (CB8657E)

Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be used with extensions.

440 Hz generator (CB12300E)
The crystal in this circuit is 32.758 kHz used in TV. The circuit was obtained in an English...
LED Bargraph (CB10830E)
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
ICL7660 Positive Voltage Multiplier (CB25848E)
This very low current circuit was found in the April 1995 issue of Electronics Now magazine. The...