We found this circuit in an Australian documentation from 1991. The circuit is suitable for SMD mounting thus making it very small. The circuit was sold in a kit at the time.
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....
This tone-modulated transmitter was found in recent English documentation. The circuit operates in the 27...
This very low current circuit was found in the April 1995 issue of Electronics Now magazine. The...