Found in a PE Hobbyst Handbook of 1991, this circuit was originally proposed to time photographic baths in developing rooms but can be used for other purposes. The circuit beeps at 30-second intervals.
This circuit with 5 V power was suggested by Motorola's Linear Databook of 1990. The circuit has...
We found this circuit in a 1982 documentation. An intercom to be good must be sensitive and have...
This circuit is indicated to determine the flight time of an electric motor model airplane. The...