This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an auxiliary relay with the call signal for a possible louder bell.
This simple injector circuit can actually be powered by voltages from 3 to 9 V. The frequency is...
Found in a 90s R-E Experimenters Handbook, this circuit amplifies signals from 100 Hz to 3 MHz....
This circuit was obtained from a manual of the integrated circuit itself, but can be applied to...