Using a dual 555 CMOS this very useful circuit on the bench was found in the July 1998 Electronics Now magazine. The circuit is battery powered.
This circuit generates a sinusoidal signal with only -80 dB THD. The circuit was found in a 90's...
This circuit is from a 1980s Motorola documentation. The circuit can be set to fire from 60 to 120...
If interference occurs in several receivers, much more interesting than placing a filter on each...