delayed output timer

Thread Starter


Joined Feb 2, 2012
I am looking to build an automatic controller for an audio switcher that will switch automatically upon loss of audio. The receiver provides a closed contact upon audio loss for the trigger. I need a timer circuit that will ignore short losses of less than 3 seconds, but if the loss is longer than 3 seconds it will output a pulse that can be used to make the switcher switch to backup audio.


Joined Sep 9, 2010
Not really sure if it would work, but there is a circuit known as a missing pulse detector. It can be made using the 555 timer IC. Basically, audio peaks continuously reset the timer. When audio stops and fails to reset, the timer goes through its cycle, ultimately changing the output state.