The circuit is from the 1994 National Semiconductor Linear Applications Handbook but can be implemented with more modern operational amplifiers. The power supply must be symmetrical.
Using the LM3909 this circuit was found in the January 1992 issue of Radio Electronics magazine....
This circuit allows the coding of several relays from coded keys that must be activated, according to...
To power small projects, we found this circuit in the Radio Electronics magazine of May 1977. The...