Telephone Off Hook (CB24947E)

This circuit for old lines was found in the March 1986 Radio Electronics magazine. The circuit is powered by 9 V and uses an LED indicator.

Various voltages power supply (CB20211E)
This multiple power source, with two transformers was found in American documentation from the...
Integrated Transmitter MC2833 (CB14567E)
We found this transmitter circuit with a single chip in the Motorola Linear Databook of 1990. The...
Mark and Space CMOS Oscillator (CB19233E)
This oscillator can use inverters or connected AND or NAND gates as such. The signal produced with...