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 circuit was obtained in a publication in 1976, but it can still be assembled today with the...
This circuit was obtained in an Electronque Loisirs magazine from France, in a July 1991 edition. It...
This hearing aid or stethoscope headset amplifier was found in a 1980s documentation. The...