The operational amplifier and the sensor used in this National Semiconductor circuit are not common today, but the configuration can be adapted to use current components.
We found this source with the CI 723, common at the time, in a 1989 paper. Power transistors must be...
Often, unauthorized people use the phone to make improper calls. A control for this is achieved with...
Found in an 80's documentation this circuit uses an integrated from the uncommon era today. Other...