Newbie level 5
I have a 4MHz pulse train output of a device with 50% duty cycle. I need a circuit which can turn on a relay if a pulse is missing. I can take care of the relay interfacing but need help with the detection part. I can tweak by using SPICE if I can find a generic topology. Is there a way to achieve this(for 4MHz pulse train) without using an FPGA or a microcontroller?