A simple circuit designed around the popular NE556. The NE556 consists of two NE555?s in one package. The one NE555 is used to trigger the next. The end result is then, that you get a timer that switches on/off at certain intervals.
EFK 12000 Just Whistle
EFK 12001 Infra -Red Link
EFK 12002 Infra -Red Remote Control
EFK 12004 Telephone Line Recording Switch
EFK 12005 Sound-Activated Switch