I am one the search for a product that detects an audio frequency and allows for the switching of an AC voltage. The application lies in an automated story telling system in which a tape player is controlled by a timer that is picked up after the closure of a 12VDC control circuit. The tape players utilize a 3min continuous tape and therefore the tape is to be at the beginning of the story after a single execution of the system. (with timer set to 3min)
The problem with the system is that the stories are approximately 3 min 3s in length (depending on tape player temperature, system voltage etc.). The timers therefore loose their synchronization with the system after approximately 10 uses and the closure of the control circuit then starts the story anywhere but at the beginning.
The proposed solution is to place an inaudible frequency on the tape at the end of the story. We then need a filter of some sort to sense this frequency then relay the power supply to the timer (120VAC, 1A). We are looking for a prefabricated device that could perform this task for us.
We are looking to fix this problem without having to replace the existing equipment. We are in search of approximately 10-15 units. If you have any products that can perform this job please respond to this letter so that we can look into the product.
Thank you for your time,