This circuit for testing old analog lines was published in April 1986 Radio Electronics magazine. The circuit uses only passive components.
We found this circuit in a William Sheets. The circuit is for frequencies up to about 500 kHz. |...
We found this circuit in a Motorola manual. The circuit has the capacitor charging at 15 to 30 V,...
Using an old integrated circuit, this low power amplifier, on the order of a few watts, includes tone...